In a shift in position, Obama said he would sign a short-term measure keeping the government running even without an agreement to give negotiations more time to succeed.
At the White House, a senior budget official said the impact of a shutdown "will be immediately felt on the economy."
For all the tough talk, it did not appear the two parties were too far from a deal.
Officials in both parties said that in the past day or so, Democrats had tacitly agreed to slightly deeper spending cuts than they had been willing to embrace, at least $34.5 billion in reductions.
Agreement on that point was conditional on key details, but it was a higher total than the $33 billion that had been under consideration.
It also was less than the $40 billion Boehner floated earlier in the week — a number that Republicans indicated was flexible.
There also were hints of Republican flexibility on the ban they were seeking to deny federal funds to Planned Parenthood. Officials said that in talks at the White House that stretched on after midnight on Wednesday, Republicans had suggested giving state officials discretion in deciding how to distribute family planning funds that now go directly from the federal government to organizations such as Planned Parenthood.
That would presumably leave a decision on funding to governors, many of whom oppose abortion, and sever the financial link between the federal government and an organization that Republicans assail as the country's biggest provider of abortions.
Associated Press writers David Espo, Jim Kuhnhenn and Darlene Superville contributed to this report.
Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
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