Sen. John McCain said Thursday the Senate could not overcome an impasse on debates and voting for controversial amendments to its 2018 defense policy bill, including a measure to eliminate sequestration.

The sequestration amendment, sponsored by Sen. Tom Cotton, R-Ark., is among four amendments the upper chamber was trying to bring to the floor for votes since Wednesday as part of passing the National Defense Authorization Act, but could not reach a consensus to allow it.

The other amendments deal with a prohibition on indefinite detention of terrorist suspects, foreign goods in the defense supply chain, and limitations on medical research funding in the Defense Department.

"It really came down to about four amendments that we could never get agreement to move forward on," said McCain, who is shepherding the bill as the Armed Services Committee chairman.

Senate Majority Leader Mitch McConnell said he intended to file a motion to end debate on the defense bill Thursday afternoon, which could lead to a final vote early next week.

The Senate did agree to add 104 noncontroversial amendments to the NDAA without debate and it appeared more could be added. Those would be passed along with the bill during a final vote.

"We are still continuing to work together to see if there are additional amendments we can include," said Sen. Jack Reed, D-R.I., the ranking member of the Senate Armed Services Committee.

Cotton's sequestration amendment was a key sticking point, according to a congressional aide. It would have removed the legal mechanism that has enforced budget spending caps since 2013, potentially allowing the Congress to move ahead with major hikes in defense for 2018.

McCain wanted a vote on the measure but Democrats opposed consideration on the floor, according to a congressional aide.

Senate Majority Whip John Cornyn said Thursday it was time to remove the sequester because it has hampered the military's ability to plan and contributed to what many believe is a crisis of readiness in the armed services.

"One thing I cannot defend is how we continue to tie our own hands when it comes to funding the United States military," Cornyn said.