The congressional effort to reverse the "don't ask, don't tell" policy on gays and lesbians in the military has landed on the desk of Rep. Patrick J. Murphy (D-Pa.), an Iraq war veteran and Bronze Star recipient who Democrats hope will give the legislation new momentum in the House.

Murphy takes over as the lead sponsor of the bill from former Rep. Ellen O. Tauscher (D-Alamo), who retired Friday to take a position in the Obama administration.

The shift comes as gay rights advocates are pressing President Obama to make good on a campaign promise to repeal the 16-year-old rule that bars gays in the military from disclosing their sexual orientation. At the same time, the administration is looking to Congress to reverse the law and says it is considering dealing with the issue more humanely in the interim.

"It is vital to our national security," Murphy said Wednesday of the Military Readiness Enhancement Act. "We have troops that are fighting in two wars, and we need every qualified, able-bodied individual" who wants to serve.

Since "don't ask, don't tell" was enacted in 1993, about 13,000 military personnel have been discharged because of their sexual orientation.

With Murphy, 35, the Democratic leadership has an aggressive two-term lawmaker who in 2006 was the first Iraq war veteran elected to Congress. A former prosecutor and West Point professor, Murphy was a captain in the Army's 82nd Airborne Division.

He said he anticipated a struggle to rally enough support to bring the bill to the floor. "This is going to take months and months, but change is going to happen."

The legislation's prospects are similarly uncertain in the Senate, where Sen. Edward M. Kennedy (D-Mass.), who is suffering from a brain tumor, is expected to take the lead.

Opponents are readying their own fight, arguing that gays' open service would hurt national security.

"Our national security depends on the men and women of the military," Elaine Donnelly, president of the Center for Military Readiness, said in testimony before Congress last year. "For our own sake as well as theirs, the United States armed forces must be constructed on foundations that are sound."

The organization was behind a letter sent to Obama this year urging continued support for "don't ask, don't tell" that was signed by more than 1,000 officers from all branches of the military.

Public opinion appears to side with changing the policy. A Gallup poll in May found that 69% of Americans favored allowing gays and lesbians to openly serve in the military. About a quarter of respondents -- 26% -- were opposed.

The Obama administration has been cautious in its approach, perhaps wary of President Clinton's experience in 1993. Clinton stumbled through his first year in office in part because of the emphasis he placed on trying to allow gays to serve openly in the military.

A May report by the UC Santa Barbara's Palm Center asserted the president had the power to stop the military from discharging service members for their sexual orientation. But the White House has said it was focusing on a "legislative vehicle" to deal with the issue.

At an event Monday, Obama said his office was working with the Pentagon and members of Congress on how to end the rule.

"Someday, I'm confident, we'll look back at this transition and ask why it generated such angst," Obama said. "But as commander in chief in a time of war, I do have responsibility to see that this change is administered in a practical way."

Defense Secretary Robert M. Gates said this week that he wanted to make the law dealing with gays in the military "more humane" until Congress acted. Among the ideas under consideration: The military might not have to expel someone whose sexual orientation is revealed by a third party out of vindictiveness or suspect motives.