President Biden said Wednesday he’s willing to scale back a proposed corporate tax increase in his massive infrastructure plan amid resistance from a key Senate Democrat and a new study that said the plan would sap wages and economic growth in the long run.

Mr. Biden challenged opponents of the $2.25 trillion plan to put up or shut up on outlining their own ideas, while the Treasury Department projected the broader plan translates to roughly $2.5 trillion in tax hikes over 15 years.

“I’m wide open, but we got to pay for this,” Mr. Biden told reporters when asked about a corporate tax rate lower than the 28% that is in his plan. “I’ve come forward with the best, most rational way — in my view, the fairest way — to pay for it. But there are many other ways as well, and I’m open.”