General James Amos, the new commandant of the U.S. Marine Corps, said Sunday that he opposes repeal of “Don't Ask, Don't Tell,” the 1993 law that bans gay and bisexual troops from serving openly.

Amos, who replaced retiring General James Conway, who also opposes repeal, told the Los Angeles Times his objections to repeal stem from “combat effectiveness.”

“There's a risk involved,” Amos, who assumed the helm two week ago, said. “I'm trying to determine how to measure that risk. This is not a social thing. This is combat effectiveness.”

Amos is at odds with Secretary of Defense Robert Gates and President Barack Obama, both of whom have urged Congress to repeal the policy.

Gates told reporters on Saturday that he would like to see repeal happen in the upcoming lame-duck session of Congress, then added, “but I'm not sure what the prospects for that are.”

During a post-election news conference on Wednesday, the president said he sees an opportunity to repeal the ban after the Pentagon delivers its study on repeal. The study, which is due on December 1, includes a controversial survey of how troops and their families feel about the issue. “That will give us time to act, potentially, during the lame-duck session to change this policy,” he said.

Amos argued that there is no parallel in civilian life to the military.

“We're talking about young men – laying out, sleeping alongside of one another and sharing death, fear and loss of brothers,” he said.

Supporters of repeal are also urging Congress to act before new members take their seats in January, potentially closing the door on legislative repeal for the next two years.

“The Senate should call up the defense bill reported out of committee and pass it before it goes home for the year,” Aubrey Sarvis, executive director of Servicemembers Legal Defense Network (SLDN), the largest group lobbying for repeal, said in a statement. “If the president, Majority Leader [Harry] Reid, Secretary Gates, and a handful of Republican senators are committed to passing the comprehensive defense bill, there is ample time to do so.”

“Any talk about a watered down defense bill, whereby the 'Don't Ask' revisions would be stripped out, is unacceptable and offensive to the gay and lesbian service members who risk their lives every day,” he added.

Republicans will take over control of the House in January, and increase their numbers in the Senate, making repeal much more difficult. Arizona Senator John McCain has already pledged to filibuster any attempt at repealing the Clinton-era policy.