The pressure is on for the U.S. House of Representatives, whose lawmakers are meeting Saturday in another effort to pass a federal budget and avoid a government shutdown.
Congress has until Monday at midnight to approve a bill providing funds to keep the government running from October 1 onward.
The Republican-controlled House has already rejected a bill the Senate sent Friday that would keep the government running through November 15. That bill did not include a provision to de-fund President Barack Obama's health care reform law, a goal of many Republican lawmakers.
The House is now set to vote later Saturday on its own version of the budget, expected to include a provision that would postpone the health care law for one year. But with the Democratic-led Senate insisting it will not pass a bill that alters the law -- known formally as the Affordable Care Act, but nicknamed "Obamacare" -- it is unclear what might happen come Monday.
If the two houses of Congress cannot make the midnight deadline, hundreds of thousands of federal workers will be temporarily laid off and many government programs halted.
Lawmakers from both parties engaged in a spirited House debate Saturday, urging each other to make compromises.
On Friday, President Obama told White House reporters that Republicans in the House should stop what he called "political grandstanding'' and approve a temporary government funding measure without tying it to efforts to gut the new health care law.
The House of Representatives Speaker, Republican John Boehner, accused the president of "grandstanding" himself, saying Mr. Obama has refused to even be part of the process.
Another deadline also looms -- October 17 -- when Congress must vote to increase the government's borrowing authority. If no agreement is reached by then, the United States could default on its debts for the first time ever.
President Obama said Friday that a failure by Congress to increase the so-called "debt ceiling" would have a "profound destabilizing effect" on the U.S. and world economies.
Some Republican leaders fear a partial shutdown of the federal government would hurt the party's standing heading into next year's congressional elections. A government shutdown in the mid-1990s, when Republicans controlled both houses of Congress, was followed by the re-election of then-president Bill Clinton in 1996.