House Republicans turned up the political heat by passing a spending plan that defunds President Barack Obama's health care law, a ploy that pushes government toward shutdown and possible default.
Congress now has just nine days to breach a bitter ideological divide and approve a short-term federal budget before several government agencies and programs shutter at the beginning of fiscal year 2014 on October 1.
Lawmakers voted Friday along party lines 230-189 to fund government operations at current levels through December 15, setting up a showdown with the Democratic-led Senate, which will consider -- and almost certainly reject -- the measure next week.
The Republican bill includes a provision that strips funding for the health care law, which its critics have nicknamed "Obamacare" and which the GOP has fought to repeal since its passage more than three years ago.
Speaker John Boehner, whom Democrats accuse of caving in to extremists in his caucus, insisted the vote reflected Americans' frustration with ill effects of the health law.
"Our message to the United States Senate is real simple: the American people don't want the government shut down, and they don't want Obamacare," Boehner said, to loud cheers from his Republican members.
But with both sides insisting they will not blink in the face-off, the nation careened into fiscal whitewater.
"We really have no idea -- no idea -- how this is going to play out yet," a Republican congressional aide told AFP.
Obama looked beyond the shutdown threat to a more portentous battle next month -- the need to raise the US borrowing limit, which Republicans have also vowed to try and block unless the health care law can be delayed by a year.
The president, visiting a car plant in Missouri, accused Republicans of risking a "tailspin" for the still recovering US economy by putting partisan zeal ahead of the good of the nation.
"If we don't raise the debt ceiling -- we are deadbeats," Obama warned in a fiery speech, saying it was "the height of irresponsibility" for House Republicans to threaten a government default unless they get their way.
Later, he telephoned Boehner to urge the House leader to fulfill Congress's role in paying the nation's bills, but Obama also said he "wouldn't negotiate with him on the debt limit," according to a Boehner aide.
"The speaker was disappointed but told the president that the two chambers of Congress will chart the path ahead," the aide added. "It was a brief call."
Democratic Senate Majority Leader Harry Reid has promised defeat of the measure in his chamber, saying Republicans faced a stark choice: "pass a clean bill to fund the government, or force a shutdown."
All but one House Republican voted for the bill, which earned the support of just two Democrats from relatively conservative districts.
The Senate will likely approve a short-term budget with no Obamacare provision and send it back to the House, putting the Republican leadership under intense pressure to pass it -- or revisit the health care debate and risk a potentially devastating shutdown.
House Democratic leader Nancy Pelosi has warned that the GOP's Tea Party faction is "playing with fire," and on Friday she said it was time to "get our House in order" and avoid another fiscal crisis.
"What is brought to the floor here today is, without a doubt, a measure designed to shut down government. It could have no other intent," she fumed.
As lawmakers bickered, freshman Democrat Eric Swalwell took to the House floor to berate the "radical right wing effort to walk our economy off a cliff."
Republicans, he added colorfully, should "wake up from this radical, ideological wet dream."
The US government is expected to run out of money by around October 15 -- a scenario that could send stock markets tumbling and shockwaves coursing through the global economy.
While several Senate Republicans have publicly urged their House colleagues to back off their threat to create a fiscal nightmare if they don't get Obamacare defunded or delayed, some insisted there was no better time to press their case.
Senator Ted Cruz, a favorite of the right-wing Tea Party movement, said "I will do everything necessary and anything possible to defund Obamacare," including a filibuster aimed at blocking legislation from progressing through the Senate.
House conservatives swatted away concerns that it was the wrong time to dwell on health care, given the precarious fiscal challenges in the immediate future.
"We are criticized for voting to repeal Obamacare 35 times when it didn't matter," congressman Marlin Stutzman told AFP.
"If we don't vote to defund it when it matters, then we might as well all go home."