Until recently, debt-limit increases have not been the target of filibusters; the first in memory came four years ago, when Democrats controlled the Senate with a filibuster-proof 60 votes.
Many Republicans in the Senate, including Minority Leader Mitch McConnell of Kentucky and Whip John Cornyn of Texas, have voted for so-called clean debt-limit increases during Republican administrations.
Some Republicans seemed wary of participating in a filibuster that could rattle the stock and bond markets.
"We shouldn't be dismissing anything out of hand, whether it's the debt ceiling or what we're going to do with this government shutdown," said Sen. Lisa Murkowski, R-Alaska. "We've got a situation where you've got a calendar running, you've got people who are frustrated and upset, so let's figure it out."
The deadlock over the shutdown — sparked by House Republicans' insistence that a temporary funding bill contain concessions on the Patient Protection and Affordable Care Act, the signature legislation of Obama's first term — shows no signs of breaking, with each side repeating its talking points.
Democrats from Obama down to the most junior lawmakers said again that the House should vote immediately on ending the partial closure of the government. Obama said Boehner "doesn't apparently want to see the ... shutdown end at the moment, unless he's able to extract concessions that don't have anything to do with the budget."
Boehner, in rebuttal, called on Obama to agree to negotiations on changes in Obamacare and steps to curb deficits, the principal GOP demands for ending the shutdown, which began Oct. 1 at the beginning of the government's fiscal year, and eliminating the threat of default. "Really, Mr. President. It's time to have that conversation before our economy is put further at risk," Boehner said on the House floor.
The White House has said repeatedly the president will not negotiate with Republicans until the government is fully reopened and the debt limit has been raised. But the administration hasn't insisted that the debt-limit measure has to be completely clean of add-ons.
White House aide Jason Furman told reporters some add-ons could be acceptable if Boehner "needs to have some talking point for his caucus that's consistent with us not negotiating ... That's not adding a bunch of extraneous conditions." Another administration official, Gene Sperling, said the administration could be open to an interim, short-term debt-limit extension to prevent a catastrophic default.
Republicans were sticking with a strategy of trying to pin the blame for the shutdown on Obama for being unwilling to negotiate. The House also passed legislation Monday to reopen the Food and Drug Administration, the latest in a series of piecemeal funding bills to advance through the GOP-controlled chamber.
Meanwhile, a new Gallup poll released Monday showed the job approval rating of Congress down to 11 percent, only 1 percentage point above its all-time low. The number, down from 19 percent a month ago, according to the same poll, was largely due to a decline in approval by Democratic-affiliated respondents.
Another poll released Monday, by the Washington Post and ABC, revealed that Americans were more likely to blame congressional Republicans for the budget showdown than congressional Democrats or Obama. Only 24 percent of respondents said Republicans are handling budget negotiations favorably, compared with 35 percent for Democrats and 45 percent for the president.
Al Jazeera and The Associated Press