- Rand Paul was holding up the Senate's vote on a massive budget deal.
- Paul wants a vote on an amendment to restore budget caps, according to a spokesman.
- The government partially shuts down at midnight Thursday.
Sen. Rand Paul was blocking the Senate's move to quickly pass approve its massive budget deal Thursday with only hours until government funding lapses.
For the Senate to hold a vote on the spending package Thursday, all senators must agree. The Kentucky Republican held out as he sought a vote on an amendment to maintain budget caps.
"All Senator Rand Paul is asking for is a 15-minute vote on his amendment to restore the budget caps. He is ready to proceed at any time," Paul spokesman Sergio Gor said in a statement.
As Paul railed against lifting spending caps, the nonpartisan Congressional Budget Office estimated that the bill would cost about $320 billion. Most of that would come in the first year.
Paul, a fiscal conservative, opposes the boost to military and domestic spending proposed by bipartisan Senate leaders. The bill before the Senate would set up a roughly $300 billion increase in the budget caps over two years.
When the Senate gets to a vote, the measure appears to have enough support to pass.
"I think it will all work out. But it's up in the air," said Senate Majority Whip John Cornyn, R-Texas, according to Politico .
If the Senate approves the proposal, the House would then have to pass it before midnight Thursday and send it to President Donald Trump for his signature.
In the House, both fiscal conservatives and liberals who sought a deal to protect young immigrants from deportation threatened the plan's passage. On Thursday morning, House Speaker Paul Ryan said he believed his chamber had enough support to approve it .
Other GOP Sens. Jeff Flake of Arizona, Bob Corker of Tennessee and Steve Daines of Montana said they would oppose the plan over spending concerns.
Flake said in a statement that "fiscal responsibility is more than a talking point to trot out when the other guys are in charge."
In his statement announcing opposition, Corker said, "to say I am discouraged by the outcome of these negotiations would be an understatement."
The vast majority of the Republican lawmakers who are opposing the budget agreement, including Paul, voted for the GOP tax law. The massive tax cuts are estimated to add more than $1 trillion to budget deficits over 10 years, even after economic growth is taken into account, according to the CBO.
— CNBC's Ylan Mui contributed to this report
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