As a partial US government shutdown neared the three-week mark, Democrats on Wednesday were set to test Republicans' resolve in backing President Donald Trump's drive to build a wall on the border with Mexico, which has sparked an impasse over agency funding.
House of Representatives speaker Nancy Pelosi and her fellow Democrats who took control of the chamber last week plan to advance a bill to immediately reopen the Treasury Department, the Securities and Exchange Commission and several other agencies that have been in partial shutdown mode since 22 December.
Democrats are eager to force Republicans to choose between funding the Treasury's Internal Revenue Service - at a time when it should be gearing up to issue tax refunds to millions of Americans - and voting to keep it partially shuttered.
In a countermove, the Trump administration said on Tuesday that even without a new shot of funding, the IRS would somehow make sure those refund checks get sent.
But it was the Republican president's insistence on a massive barrier on the border that dominated the Washington debate and sparked a political blame game.
In a nationally televised address on Tuesday night, Trump asked: "How much more American blood must be shed before Congress does its job?" referring to murders he said were committed by illegal immigrants.
Senate Democratic leader Chuck Schumer, responding to Trump, said he and the president both wanted stronger border security but disagreed over the most effective approach.
"Most presidents have used (White House) Oval Office addresses for noble purposes. This president just used the backdrop of the Oval Office to manufacture a crisis, stoke fear and divert attention from the turmoil in his administration," Schumer said.
Later this week, Pelosi will force votes that one by one provide the money to operate departments ranging from Homeland Security and Justice to State, Agriculture, Commerce and Labour.
By using a Democratic majority to ram those bills through the House, Pelosi is hoping enough Senate Republicans back her up and abandon Trump's wall gambit.
The political manoeuvring comes amid a rising public backlash over the suspension of some government activities that has resulted in the layoffs of hundreds of thousands of federal workers.
Other "essential" employees are being required to report to work, but without pay for the time being.
With tempers running high over Trump's demand for $5.7 billion just for this year to fund wall construction, there are doubts Pelosi's plan will succeed in forcing the Senate to act.
Senate Majority Leader Mitch McConnell, a Republican, has not budged from his hard line of refusing to bring up any government funding bill that does not have Trump's backing.
The funding fight stems from Congress' inability to complete work by a 30 September, 2018, deadline on funding all government agencies.
It did manage, however, to appropriate money for about 75 per cent of the government by that deadline - mainly military and health-related programs.
As House Democrats plow ahead, Trump and vice president Mike Pence will go to Capitol Hill on Wednesday to attend a weekly closed lunch meeting of Senate Republicans.
They are expected to urge them to hold firm on his wall demands, even as some are publicly warning their patience is wearing thin.
Later in the day, Trump is scheduled to host bipartisan congressional leaders to see if they can break the deadlock. On Thursday, Trump travels to the border to highlight an immigration "crisis" that his base of conservative supporters wants him to address.
But so far, there have been few signs that either Trump or his Democratic opponents in Congress are moving toward a deal.