Sen. Rand Paul, a libertarian who advocates for reduced federal spending, on Thursday night was blocking a spending bill that must pass by midnight, a move that has the potential to cause a brief government shutdown.

A temporary funding measure expires at midnight, and lawmakers were prepared to pass a bill to both fund the government through March 23 and outline a spending cap deal that would enable spending accords for the next two years.

Paul, R-Ky., is demanding a vote to restore federal budget caps that the deal obliterates.

Republican leaders won't allow the vote, arguing it would open the bill up to other amendments.

But Paul is refusing to give in, and in a Senate floor speech, argued that Republicans are ignoring the growing debt now that they're in power, even though they railed against the debt when President Obama was in office.

"I want people to feel uncomfortable," he said of his fellow senators. "I want them to have to answer people at home who said, 'How come you were against President Obama's deficits, and then how come you're for Republican deficits?'"

The delay was prompting the Trump administration to prepare for a possible shutdown.

"The Office of Management and Budget is currently preparing for a lapse in appropriations," an OMB official said. "As we stated earlier today, we support the Bipartisan Budget Act and urge Congress to send it to the president's desk without delay."

Unless he relents, the soonest the Senate can vote on the spending bill is 1 a.m. — an hour after the midnight spending deadline. The House then would have to consider and pass the bill before sending it to the desk of President Trump.

The impasse makes it likely the government will face a brief, partial closure, assuming both chambers are able to pass the legislation, which also suspends the debt ceiling for one year and provides more than $80 billion in disaster relief aid to states and territories.

The partial closure, however short, would be the second in two months.

Democrats triggered a three day shutdown in January when they opposed passing a short term spending bill because it excluded a provision to protect so-called Dreamers.

Paul went to the Senate floor and highlighted charts showing the government's fiscal situation during a speech in which he argued that Congress is spending the nation into significant debt.

The budget deal busts the budget caps imposed in 2011 by $37 billion for domestic programs and $54 billion for military programs over two years.