After pushing the deadline back for funding portions of the government by two weeks - the original deadline was December 7 - Congress and the White House have fewer than 96 hours to reach an agreement before the clock struck midnight on Friday and vast sections of the government run out of funding.
Democrats are united in their opposition to Trump's ask, saying their intent is to vote for no more than $1.6 billion in border security funding as laid out in bipartisan Senate legislation earlier this month.
The White House showed its willingness to budge as it became apparent the president does not have support in Congress for funding the wall at the $5 billion level he wants.
"We'll see what happens", Trump said Tuesday after a school safety event.
Since then, a senior House Republican aide said his party was "in a pickle" over how to keep the government open.
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And the Alabama Republican said he assumed that President Donald Trump would sign the bill.
Sanders' comments come after a series of miscalculations by the White House and Republicans in recent days over how to try to get Democrats to sign on to US$5 billion to pay for the construction of Trump's long-promised wall along the Mexico border. About 75 percent of the government is already funded through September 2019.
Congressional leaders say they are opposed to a shutdown. If Congress and the White House agree to a short-term funding patch that could leave the issue for the new, incoming Congress to resolve in January.
"We're looking at the other options", Sanders told reporters.
"The president has asked every agency to look and see if they have money that they can use for that goal", White House press secretary Sarah Huckabee Sanders said Tuesday. "At the end of the day, we don't want to shut down the government".
"I'll tell you what, I am proud to shut down the government for border security, Chuck", Trump told the top Senate Democrat. "We ought not accept a CR until we exhaust every other opportunity to solve the appropriations".
While border security experts don't necessarily support a wall from Tijuana all the way to the Gulf of Mexico, many agree that there are plenty of areas that now lack a physical barrier and could use one. "Everyone knows-just good common sense-we should be able to secure our southern border". Many Republicans say it's up to Trump and Democrats to cut a deal.
About half the workers would be forced to continue working without immediate pay.
Mr Trump has previously said the wall would cost $25bn.