WASHINGTON - The United States must add at least 7,000 troops in Afghanistan, double foreign aid spending to $50 billion, and be prepared to strike unilaterally against terrorist sanctuaries in Pakistan, Senator Barack Obama of Illinois said yesterday in a major speech laying out his counterterrorism plan.

The thrust of Obama's 35-minute address on national security was that America is less safe today than it was before the Sept. 11, 2001, terror attacks. He argued that the "misguided" war in Iraq and the sacrifice of American values in military detentions have sparked fresh anti-Americanism and diverted attention from the crucial task of bringing Al Qaeda leader Osama bin Laden and his followers to justice.

"When I am president, we will wage the war that has to be won," Obama said to a roomful of journalists and scholars at the Woodrow Wilson International Center for Scholars.

Obama delivered his speech, in which he outlined a robust foreign policy with several military and diplomatic components, amid a fierce debate with presidential rival Hillary Clinton about when it is appropriate for a US president to meet with leaders of rogue nations such as Syria and Iran. Obama continued to sharpen their differences yesterday by obliquely equating the New York senator's reticence to meet with such leaders with the policies of President Bush, which he said has failed.

"It's time to turn the page on Washington's conventional wisdom that agreement must be reached before you meet, that talking to other countries is some kind of reward, and that presidents can only meet with people who will tell them what they want to hear," Obama said.

Political analysts interpreted Obama's speech as a pointed message to his presidential competitors: that he will not accept being portrayed as weak or inexperienced on terrorism and world affairs. Within hours of his remarks, however, the campaign of one of those competitors, Senator Joseph R. Biden Jr. of Delaware, dubbed Obama a "Johnny-come-lately" and said Obama had contributed little in recent months while Biden has worked toward many of the same goals.

Much of Obama's speech was devoted to how the United States should use nonmilitary means to rebuild relationships around the world. He vowed to attend a "major Islamic forum" in his first 100 days in office. He called for a new $2 billion global education fund to combat the influence of radical Islamic schools. And he said he would launch a public diplomacy initiative consisting of "America Houses" across the Islamic world with the "Internet, libraries, English lessons, stories of America's Muslims and the strength they add to our country, and vocational programs."

But though Obama proposed billions in new spending, he did not detail yesterday how he would pay for it. Aides said that drawing down the US military presence in Iraq would free up billions.

One striking element of the speech was Obama's tough rhetoric on Pakistan, which he said must do more to root out terrorists hiding in its remote regions or lose American aid. And he said that if Pakistan's president, General Pervez Musharraf, was unwilling to go after high-level terrorist targets despite "actionable intelligence," the United States would act on its own.

"I understand President Musharraf has his own challenges," Obama said. "But ... there are terrorists holed up in those mountains who murdered 3,000 Americans. They are plotting to strike again."

Husain Haqqani, director of the Center for International Relations at Boston University and a former adviser to several Pakistani prime ministers, said Obama was right to address forthrightly Pakistan's role in battling terrorism. But, he said, the United States had to be absolutely sure of its target or a unilateral military strike could backfire.

"It sounds very good to say we're going to go in and strike, but who are you striking and what are you striking?" Haqqani said. "All you're going to do is turn people against the US."

Senator Chris Dodd of Connecticut, who is also running for the Democratic nomination and trying to get traction, was unusually critical of Obama's remarks on Pakistan, saying it was "dangerous and irresponsible to leave even the impression the United States would needlessly and publicly provoke a nuclear power."

Obama was introduced by Lee Hamilton, a former US representative from Indiana who helped lead the 9/11 Commission and the Iraq Study Group. Hamilton has not endorsed a candidate, but he gave Obama's speech high marks afterward, calling it "very well done."

"I'm very impressed with the number of quite constructive proposals he had in the speech," Hamilton said, highlighting Obama's strong warning to Pakistan. "It seems to me if we've learned anything at all about fighting terrorism, we have learned that we cannot permit Al Qaeda to have sanctuaries, and those sanctuaries must go."

In another veiled jab yesterday at Clinton, Obama stepped up his criticism of Congress's 2002 vote authorizing Bush to invade Iraq. "Congress rubber-stamped the rush to war," he said, also dubbing Congress "coauthor of a catastrophic war."

Scott Helman can be reached at shelman@globe.com.

WASHINGTON - In July of 2004, the day after his speech at the Democratic convention catapulted him into the national spotlight, Barack Obama told a group of reporters in Boston that the United States had an "absolute obligation" to remain in Iraq long enough to make it a success.

"The failure of the Iraqi state would be a disaster," he said at a lunch sponsored by the Christian Science Monitor, according to an audiotape of the session. "It would dishonor the 900-plus men and women who have already died. ... It would be a betrayal of the promise that we made to the Iraqi people, and it would be hugely destabilizing from a national security perspective."

The statements are consistent with others Obama made at the time, emphasizing the need to stabilize Iraq despite his opposition to the US invasion. But they also represent perhaps his most forceful language in depicting withdrawal from crisis-ridden Iraq as a betrayal of the Iraqi people and a risk to national security.

Obama spoke out passionately against the war in 2002 as an Illinois state senator, while many in Congress were silent. But his thinking on how to resolve the crisis in Iraq evolved.

During his 2004 Senate race, he supported keeping troops in Iraq to stabilize the country. But starting in 2005, as violence engulfed the country, he grew increasingly disillusioned.

Now, Obama's views about the war have become a campaign issue, as Hillary Clinton - who voted for the war's authorization - has questioned whether Obama has been consistent in opposing the war.

Her husband, Bill, said Obama's depiction of his longstanding opposition to the war was a "fairy tale." And yesterday, news of an Obama adviser's comments that his promise to withdraw troops within 16 months represented only a "best-case scenario" further fanned questions about his Iraq views.

Yesterday, Obama struck back, declaring that Clinton "doesn't have any standing to question my position on this issue." And he added that, "I will bring this war to an end in 2009, so don't be confused."

In 2004, while supporting the Democratic presidential nominee, John F. Kerry, Obama endorsed Kerry's view that the United States had too much at stake in Iraq to withdraw at that time. Since joining the Senate in 2005, Obama has taken incrementally tougher positions on Iraq, even as he sought to hear from a wide variety of voices about what should be done there, according to aides, advisers, and transcripts of his speeches.

In November of 2005, after it had become clear that US troops faced a raging insurgency, Obama argued in a speech before the Chicago Council on Foreign Relations that the US military should scale down its presence, but that US troops were "still part of the solution" in Iraq.

"We have to manage our exit in a responsible way," he told the council, "at the very least taking care not to plunge the country into an even deeper and perhaps irreparable crisis."

In January of 2006, Obama took his first trip to Iraq, staying two days, and while there he heard conflicting views on whether US troops should stay or go.

He expressed frustration with the failure of Iraqi leaders to resolve key disputes, telling reporters that "if we have not seen significant progress over the next few months, we need to have an honest conversation with Iraqis as to what our investment is."

But 2006 unfolded as a year of sectarian bloodshed, deepening Obama's conviction that the US effort was being squandered. He began to call for a timetable for the withdrawal of US troops. By that time, the call was far from unusual, however; other senators had called for a phased withdrawal earlier.

"The notion that the United States can't be more committed to the future of Iraq than Iraqis became much more of the prominent view" among Democrats and even some Republicans in 2006, said Rand Beers, a former foreign policy adviser to Kerry.

By November of that year, voters across the nation expressed anger over Iraq, handing control of Congress to Democrats.

A month later, the Iraq Study Group recommended reducing US military support for Iraq's government if its leaders failed to make progress on achieving political agreements.

An author of that report, Benjamin Rhodes, later joined Obama's campaign as a foreign policy adviser, and Obama adopted some of the group's language in his 2007 bill calling for all combat brigades to be withdrawn by March of 2008.

As Obama mulled a presidential run, he began to reach out to a series of military leaders, including those who did not agree with him on Iraq.

When Richard Danzig, a former Navy secretary, organized two meetings for Obama with retired military officers, Danzig asked whether he should invite officers who opposed Obama's views. The answer was yes, Danzig recalled.

"One of the attractive things about Obama is the desire to get a range of views and process them himself rather than get a homogenized product or exclude people who aren't in sympathy with him," Danzig said.

In a separate meeting, Obama asked General Anthony Zinni, a critic of the war effort, what should be done in Iraq. Zinni told him: "I don't think you can abandon Iraq. The region is too important."

Despite those views, Obama's foreign policy advisory team began working on a detailed plan for bringing US troops home and managing the potential humanitarian crisis that could follow.

Obama's campaign set up a working group on Iraq, headed by Colin Kahl, a security studies professor at Georgetown University. In July 2007, Obama's top advisers and Iraq specialists, including Kahl, produced a memo that shaped Obama's core Iraq views, made public in a Sept. 12 speech: to bring home one to two combat brigades each month, with all brigades out in 16 months, and keep only a small number of troops in Iraq to protect US diplomats and launch limited, targeted strikes on Al Qaeda.

But this week, Obama adviser Samantha Power caused a stir when she told BBC's "Hard Talk" that Obama "will revisit" the plan when he becomes president.

"You can't make a commitment in March of 2008 about what circumstances are going to be like in January 2009," said Power, who resigned from the campaign yesterday over separate comments insulting Clinton. "He will, of course, not rely upon some plan that he has crafted as a presidential candidate or a US senator. He will rely upon an operational plan that he pulls together in consultation with people on the ground."

Obama insisted yesterday he would stick to his plan. But Walter Russell Mead, a fellow at the Council on Foreign Relations, said voters should expect Obama's views on the war to shift.

"If you look at Obama's stands, he has taken different stands, or differently nuanced stands, based on his perceptions of the changing realities on the ground," Mead said. "As a rational human being, [if he is elected president] nine months from now, he'll have to do the same thing. He'll have to look carefully at the situation as it is, and make the best policy calls that he can."