Sen. John McCain said Wednesday that the Senate's annual defense policy bill was being held up on the chamber floor due to a disagreement over four proposed amendments.

The impasse might lead to Senate Majority Leader Mitch McConnell invoking cloture, a procedural move that could delay the National Defense Authorization Act for days and quash expected debate on those four amendments and others filed in recent weeks, McCain, R-Ariz., the Armed Services Committee chairman, said on the Senate floor.

"I hope overnight my colleagues on both sides will sit down and figure out, as we have a number of amendments, a way that we can reach a point where we have up or down votes on these amendments that are important to the nation," he said.

The four amendments were filed by Sen. Tom Cotton, R-Ark., to end threats of sequestration cuts to the federal budget; Sen. Mike Lee, R-Utah, to prohibit indefinite detention of terrorism suspects; Sen. Tammy Baldwin, D-Wis., to protect the defense supply chain from foreign goods; and Sen. Dick Durbin, D-Ill., to preserve defense medical research programs, according to a congressional aide.

The Senate is now trying to reach a final agreement on whether the amendments will be considered or added to the NDAA bill. If it fails to agree by Thursday, the cloture motion could scuttle any chance to bring those and other amendments to the floor for debate and roll call votes.

"I must say we are at an impasse on about four amendments, all four of which are very important amendments, and we simply can't get agreement," McCain said.