Sixteen members of the Senate Armed Services Committee support repeal of the law that bans gay troops from serving openly, one more than needed for repeal language to be attached in committee, proponents say.

Committee members are expected to vote on attaching repeal language to next year's defense budget on Thursday after Democratic leaders and the White House agreed to a compromise plan to repeal “Don't Ask, Don't Tell” but delay its implementation until after the Pentagon completes its application study due at the end of the year.

On Tuesday, Maine Senator Susan Collins became the first – and so far only – Republican to break from her party and declare she would vote in favor of repeal.

Other notable Republicans on the panel – Senators John McCain and Lindsey Graham – said they oppose any effort to repeal the law until after the Pentagon completes its review.

“I cannot over emphasize the importance of completing the comprehensive review prior to taking any legislative action,” McCain wrote in a letter addressed to committee chairman Senator Carl Levin, a Michigan Democrat. “Our military is currently engaged in two wars and we must have a true assessment of the impact of repealing 'Don't Ask, Don't Tell' on the battle effectiveness prior to taking any legislative action.”

Republicans, including McCain and Roger Wicker, have threatened to filibuster the defense authorization bill on the Senate floor if it includes repeal language.

Once the repeal measure has been attached in committee, Republicans would need to round up a 60-vote majority to untie the amendment in the Senate, which includes 41 Republican members.

Several moderate Democrats, including Senators Robert Byrd of West Virginia and Ben Nelson of Nebraska, were persuaded to come off the fence and support repeal after the president and the Pentagon backed the compromise agreement on Monday.

“I did not want to blindly assent to repealing this law without giving the Congress an opportunity to re-examine the concerns of our Armed Forces and the manner in which they are being addressed,” Byrd told CNN.

Repeal boosters also believe they can count on Senator Evan Bayh from Indiana to vote favorably.

The House is also expected to take an initial vote on the issue Thursday or Friday. Pennsylvania Representative Patrick Murphy, an ardent supporter of repeal and the lead sponsor of the measure in the House, said Tuesday that by his head count the measure will sail through the House.

“We have the votes to get this done,” the Army vet said. “I have 192 co-sponsors [in the House] and commitments from dozens of others.”