WASHINGTON (AP) — A Senate vote on a wide-ranging defense policy bill was delayed Thursday after Kentucky Republican Rand Paul objected to the measure, casting the next steps in doubt and raising the slim prospect of a government shutdown if a short-term spending bill caught up in the dispute is not approved by Friday.

Paul said on the Senate floor that he opposes a provision in the defense bill that would limit President Donald Trump’s ability to draw down U.S. troops from Afghanistan and Germany. His objections threatened another must-pass bill, a one-week spending measure that would keep the government open through Dec. 18. The House has passed the stopgap measure, but a government shutdown would occur if the Senate does not act on it by midnight Friday.

Paul said he would drop his objection if GOP leaders allowed a final vote on the National Defense Authorization Act on Monday. Senators from both parties were eager to finish work on the bill this week.

South Dakota Sen. John Thune, the No. 2 Senate Republican, said he thought Paul — who has provoked government shutdowns before — was using the time-crunch for maximum leverage to remove the provision on troop withdrawals.

“I think he’s just trying to figure out ways to derail the bill. And when you’re in the U.S Senate that’s your prerogative. But most of our people would like to get it done” Thursday, Thune said.

“His thing is just to delay this and use all the time so it pushes the vote on (the defense bill) into next week, which pushes the override vote” on a possible Trump veto into the following week, Thune said of his fellow Republican, Paul.

Paul said he is concerned that the troop-amendment “creates 535 commanders-in-chief in Congress” and hampers the president’s ability to deploy troops as he sees fit. Democrats support the measure because they oppose Trump, Paul said, but the amendment would also apply to future presidents, including President-elect Joe Biden.

Paul attacked the author of the troop amendment, Rep. Liz Cheney, R-Wyo., saying she and her father, former Vice President Dick Cheney, share a neoconservative belief in “perpetual war.”

“The philosophy of these people is about war and substantiating war and making sure that it becomes and is perpetual war,” Paul said.

Cheney hit back on Twitter, charging that Paul was “currently holding up passage of the #NDAA, blaming America, and delaying hazardous duty pay to hundreds of thousands of our service members and their families. Inexcusable.”

She added: “Rand and I do have one thing in common, though. We’re both 5’2” tall.”

The dispute over the defense bill came after Senate Majority Leader Mitch McConnell, in a rare break with Trump, urged passage of the measure despite Trump’s threat to veto it.

McConnell, R-Ky., said Thursday that it was important for Congress to continue a nearly 60-year streak of passing the National Defense Authorization Act, which affirms 3% pay raises for U.S. troops and authorizes billions in military programs and construction.

“This NDAA will unlock more than $740 billion for the training, tools and cutting-edge equipment that our service members and civilian employees need to defend American lives and American interests,” McConnell said in a Senate speech ahead of an expected vote Thursday or Friday. ”It will give our troops the 3% pay raise they deserve. It’ll keep our forces ready to deter China and stand strong in the Indo-Pacific.”

The Democratic-controlled House overwhelmingly approved the defense bill on Tuesday, defying Trump’s veto threat and setting up a possible showdown with the Republican president in the waning days of his administration.

A total of 140 Republicans joined 195 Democrats in backing the bill, which received support from more than 80% of the House — well above the two-thirds support required to override a potential veto.

Trump has vowed to veto the bill unless lawmakers clamp down on social media companies he claims were biased against him during the election. Trump also wants Congress to strip out a provision of the bill that allows renaming of military bases that now honor Confederate leaders.

McConnell did not address Trump’s veto threat, but said the bill “will secure President Trump’s major progress at modernizing our capabilities, our technologies and our strategic nuclear deterrent.”

The bill “does not contain every policy that either side would like to pass. But a huge number of crucial policies are included and a lot of bad ideas were kept out,” McConnell said.

Trump tweeted Tuesday that he will veto “the very weak” defense bill unless it repeals Section 230, a part of the communications code that shields Twitter, Facebook and other tech giants from content liability.

The dispute over social media content — a battle cry of conservatives who say the social media giants treat them unfairly — interjects an unrelated but complicated issue into a bill that Congress takes pride in having passed unfailingly for nearly 60 years. It follows Trump’s bid over the summer to sabotage the package with a veto threat over Confederate base names.

If he does veto the defense bill, Congress could cut short its Christmas recess to hold override votes, senior House members said.

“I think we can override the veto, if in fact he vetoes,” House Majority Leader Steny Hoyer, D-Md., said Tuesday. “I hope he does not veto. I hope he reconsiders. And I think he will get substantial pressure (from Republicans) that, you know, you don’t want to put the defense bill at risk.″

The defense measure guides Pentagon policy and cements decisions about troop levels, new weapons systems and military readiness, military personnel policy and other military goals. Many programs can only go into effect if the bill is approved, including military construction.