President Obama warned House Republicans they would be engaged in the "height of irresponsibility" if they failed to pass a funding bill that would keep the government open by midnight.
Speaking from the White House, the president told members of the GOP that they "don't get to extract a ransom for doing your job," and said that keeping the government funded was "not a concession" to the White House.
"One faction of one party, in one house of Congress, in one branch of government, doesn't get to shut down the entire government just to refight an election," Obama said.
Earlier Monday, the Senate rejected a House measure that would have delayed implementation of the president's signature healthcare law. The 54-46 party line vote returned to the House a so-called "clean" bill that would keep the government open at current spending level, but also kept ObamaCare intact.
Speaker John Boehner (R-Ohio) indicated that he would not allow a vote on that bill, saying that instead they would move to attach a one-year delay of ObamaCare's individual mandate to a continuing resolution. The plan would also include the so-called Vitter amendment, which removes healthcare subsidies for members of Congress and political appointees.
The White House has threatened to veto the latest set of House proposals.
It's unclear whether Republicans will have enough votes to pass that legislation, with some conservatives saying that it did not do enough to undermine the Affordable Care Act. With Democrats likely to vote in unison against the GOP bill, Boehner can afford only a handful of defections.
The president spent much of his speech outlining the consequences of a government shutdown, a move that seemed to betray the narrow odds of a late-hour compromise agreement.
Obama said office buildings would close, pay checks would be delayed, and vital services "would be hamstrung." He added that veterans centers would go unstaffed, while national parks, museums, and monuments would shutter.
He also noted that the federal government was the nation's largest employer, and hundreds of thousands of workers would be furloughed without pay checks.
"What will not be furloughed is the bills they have to pay," Obama said, before heading to a Cabinet meeting to discuss implementation of the shutdown.
Warning of "a very real impact on real people," the president warned that "right away" businesses would see less spending.
"All of us will be hurt greatly should Congress choose to shut the people's government down," Obama said.
Nevertheless, Obama insisted that a shutdown "doesn't have to happen."
"My hope and expectation is that in the 11th hour once again that Congress will choose to do the right thing," he said.