The delay was voted for in the House of Representatives on Saturday night
The US government is almost guaranteed to shut down on Monday night after House Republicans voted in favour of a temporary spending bill that includes a one-year delay for Obamacare.
The Republican-led House of Representatives passed the proposal by 231 votes to 192 in one of two amendments attached to a Senate spending bill passed on Friday night. "I don't think we're near the precipice of a shutdown," said House Minority Whip Steny Hoyer. "We are on the precipice."
The White House and the leader of the Democrat-controlled Senate said they would not accept the plan.
"To be absolutely clear, the Senate will reject both the one-year delay of the Affordable Care Act (Obamacare) and the repeal of the medical device tax," said Senate Majority Leader Harry Reid.
"After weeks of futile political games from Republicans, we are still at square one."
Some White House staff may be told to take leave without pay
President Barack Obama also said he would veto the plan, resulting in the federal government technically running out of money on Monday night and forcing the first partial government shutdown in almost 20 years.
Nearly a million government employees will be forced off work without pay, and museums and national parks will close.
The row between the Democrats and Republicans over government funding has been rumbling on since 2010.
Since then there have been negotiations between the parties that have led to short-term stop-gap funding bills rather than longer term budgets.
The last time the federal government shut down was under the Clinton administration in 1995, when services ground to a halt for 28 days. It nearly happened again in April 2011.
If the shutdown does go ahead then a third of the government's 2.1 million employees will be kept off work - possibly without back pay.
Obamacare has been a divisive measure among Americans
National parks and the capital's Smithsonian museums will be closed, pension and benefits cheques will be stopped and passport applications will not be processed.
While 1.4 million troops would stay at work, they would not get paid.
The Pentagon's top financial officer Robert Hale has said that high-priority missions such as Afghanistan would not be affected.
However, he said that roughly half the Defense Department's civilian work force would be place on unpaid leave.
Training and a range of maintenance work would be cancelled.
Obama has told Republicans not to 'burn the house down'
Nearly a million government employees are set to be forced off work without pay after Republicans voted to delay Obamacare.
Government agencies have compiled a list of essential workers, and critical services such as air traffic control would continue.
The Affordable Healthcare Act was passed into law in 2010 and has since been upheld by the Supreme Court.
It is a measure that has caused particular ire among Republicans and they have continually attempted to reverse it.
Mr Obama said Republicans should not threaten to "burn the house down because you haven't gotten 100% of your way".
He said: "No one gets to hurt our economy ... just because there are a couple of laws [they] don't like."
I have been saying, warning, etc and more about this for a LONG time now. Remember?
To The People Of The USA – I am sorry for what is coming
So this is it, your Country is to CLOSE. Every Government place from Schools, Libraries and more will close. This is JUST the start. I did say I was sorry for what was coming. You people need to wake up. I love you all, truly I do, but you need to know your own country, I speak to MANY on Skype and AM STUNNED about how little many of your know about even the simplest things. One person I spoke to didn't even know Obama was President, they said "I don't keep up" Well listen, time to wake up and keep up...
This is going to end very badly and be violent also, Civil War is coming, 100% You MUST prepare.
ps: I didn't enjoy this article