The Senate on Friday rejected an amendment to its annual defense authorization bill that would have blocked President Donald Trump from launching a war with Iran without congressional approval.

The issue will likely be debated next month in the House, when that chamber takes up its own version of the defense bill.

The amendment, offered by Sen. Tom Udall, D-N.M, and co-sponsored by Republicans Mike Lee of Utah and Rand Paul of Kentucky, was voted down 50-40. Due to a unanimous consent agreement, the amendment needed 60 votes to be adopted.

Friday’s vote was unusual, considering the chamber had approved the defense bill on an 86-8 vote Thursday.

But faced with the threat of Democrats filibustering the bill, Senate Majority Leader Mitch McConnell, R-Ky., earlier this week agreed to hold the vote Friday to give senators who participated in the Democratic presidential debate Thursday night a chance to vote.

Had the Udall amendment been adopted, the Senate would have agreed by unanimous consent to include it in the already-passed legislation.

On Thursday, the Senate debated the Udall amendment, largely on party lines. Republicans — with the exception of the amendment’s cosponsors — argued Congress shouldn’t restrict the president’s options, especially in the face of Iranian bellicosity. Democrats countered, saying that Congress, not the president, has the constitutional power to declare war.