The US Government has staggered into another shutdown, after an outspoken fiscal conservative in the Senate singlehandedly delayed action by Congress on a stopgap funding bill, wrapped up in a massive budget deal.
At midnight on Thursday (local time), funding authority for most federal agencies expired without any intervening action by Congress.
Missing the midnight deadline technically triggered a shutdown, but it could be brief.
The Senate was expected to approve the stopgap bill and budget deal after 1am, and send it to the House of Representatives.
Lawmakers in that chamber were deeply divided along party lines and passage was uncertain, but House Republican leaders said the package would be approved, possibly before the start of the work day.
If it is, there would be no practical interruption in federal government business. If it is not, the result would be an actual shutdown, the second of 2018, after a three-day shutdown in January.
The midnight deadline was missed because of a nine-hour, on-again, off-again Senate floor speech by Senator Rand Paul, who objected to US$300b (NZ$416b) in deficit spending in the bill.
Earlier in the evening, the White House's Office of Management and Budget said it was preparing for a shutdown, if the stopgap bill did not win passage on time in Congress.
The US Office of Personnel Management sent an email to federal government employees at 12.06am, citing the expiry of funding and advising them to consult their agencies "for guidance on reporting for duty".
Mr Paul, a Kentucky Republican, said the overall budget bill that includes the stopgap measure would "loot the Treasury".
"The reason I'm here tonight is to put people on the spot,” he said. “I want them to feel uncomfortable.”
The Senate-crafted bill, backed by President Donald Trump, would end, for many months, the fiscal policy squabbling that has consumed Congress.
But it would be costly to US taxpayers and would further underscore a fundamental shift in Republican thinking that Mr Paul was trying to draw attention to.
Once known as the party of fiscal conservatism, the Republicans and Trump approved a sweeping tax overhaul bill in December that will add an estimated US$1.5t to the national debt over 10 years.
The new budget bill would raise military and domestic spending by almost $US300b over the next two years.
With no offsets in the form of other spending cuts or new tax revenues, that additional spending would be financed by borrowed money.
"I ran for office because I was very critical of President Obama's trillion- dollar deficits," Paul said.
"Now we have Republicans hand-in-hand with Democrats, offering us trillion-dollar deficits,” he said.
“Really, who is to blame? Both parties."
House Speaker Paul Ryan, who backs the bill, predicted the Republican-controlled House would pass it.
"I think we will," he said in a radio interview. "It's going to need bipartisan support.
“We are going to deliver our share of support."