President Obama has pledged that three-quarters of the fund will be spent out in the first 18 months, Mr. Summers said in defense of the plan.

Image The House Minority leader, John A. Boehner, discussed President Obamas proposed stimulus package on Meet the Press on Sunday. Credit... Alex Wong/"Meet the Press," via Getty Images

“We believe that this is a properly sized approach to move the economy forward,” he said.

He also said that there might be additional assistance to banks beyond the $700 billion Troubled Asset Relief Program already approved by Congress. Of Mr. Obama’s plans for how the next $350 billion of TARP funding will be spent, he said, “It’s going to be very different than what you’ve seen so far,” with an emphasis on transparency, accountability, and “getting credit flowing again.”

“The next few months are, no question, going to be very, very difficult and it may be longer than that,” Mr. Summers said.

Vice President Joseph R. Biden Jr. said on Sunday that he believed that the stimulus package would ultimately pass with “fairly strong vote across the board.” “If you notice, roughly 40 percent of this entire package is tax cuts,” the vice president said on CBS’s “Face the Nation.” “That’s not what the Democrats wanted. And 60 percent of it is spending, economic stimulus. That’s not what the Republicans wanted. But we’ve come a pretty long way already. So there will be, I’m sure, more compromise.”

Mr. Boehner and other Republicans have taken issue with the large chunk of funding in the stimulus package  some $300 billion all told  that will go to shore up the budgets of states. That figure includes billions in state aid to education and such controversial pieces as millions in spending for family-planning initiatives.

House Speaker Nancy Pelosi, speaking on ABC’s “This Week,” said that the assistance to states was necessary, including the family-planning funds.

“The family-planning services reduce cost,” she said. “The states are in terrible fiscal budget crisis now, and part of it, what we do for children’s health, education, and some of those elements, are to help the states meet their financial needs.”