WASHINGTON–President Barack Obama on Saturday pledged to end a 16-year-old policy banning gay people from serving openly in the nation’s military, in a gesture to a group that provided a major source of support during his campaign.

But the president didn’t set out a timetable for reversing the policy. As a result, his pledge might not be enough to appease some in the gay community who feel that Mr. Obama hasn’t moved quickly enough to address their issues — even as his message could spark criticism from some conservatives and members of the military.

Speaking at a human-rights dinner in the capital, Mr. Obama vowed to end the Clinton-era “don’t ask, don’t tell” policy, which allows homosexuals to serve in the military, as long as they don’t disclose their sexual orientation or act on it.

The law has long been criticized by gay-rights advocates as a half-measure that doesn’t fully recognize the rights and contributions of gay service-men and women. Mr. Obama has in the past said he would work to overturn the policy.

“We cannot afford to discharge people from our ranks with critical skills,” he told a cheering crowd of about 3,000 at the black-tie event sponsored by the Human Rights Campaign, a gay civil-rights group.

Mr. Obama also appealed to Congress to repeal the Defense of Marriage Act, which limits how state and federal bodies can recognize domestic partnerships in providing government benefits. He also vowed to press for legislation that would extend health and other employment benefits to domestic partners of workers. But he again didn’t provide a timetable.

Mr. Obama’s statements are likely to be welcomed by many liberal Democrats, although some activists criticized his failure to provide more concrete details.

Kevin Nix, spokesman for Servicemembers Legal Defense Network, which represents gay and lesbian members of the military, said the president did little more than repeat his campaign pledge on the issue.  “He missed an opportunity tonight” to set a timetable, Mr. Nix said. “We’d like a bill in Congress in 2010.”

Mr. Obama’s comments could also spark criticism from conservatives and some supporters who say the administration must set priorities, as the nation grapples with continued high unemployment, a recession, and two wars.

Any attempt to change government policy concerning gay people could further divide an already polarized Congress. The administration needs lawmakers’ cooperation to pass legislation to overhaul the nation’s health-care system, a top priority for Mr. Obama. The administration is also trying to secure passage of new financial-industry regulations and could turn to Congress to request more troops in Afghanistan.

Congress passed the law popularly known as “Don’t Ask, Don’t Tell” in 1993. Subsequent efforts by then-President Bill Clinton to repeal it ran into opposition from the military and Congress, which after 1994, was controlled by Republicans.

It’s far from clear when, or if, Mr. Obama’s pledge would have any practical impact on the armed forces. Besides that the president didn’t give a timeline for his pledge, eliminating the “don’t ask, don’t tell” rule would also require congressional action. Lawmakers may be unwilling to take up such a politically contentious issue while they tackle health-care legislation and other matters.

Advocates of repealing the rule point to polling data showing that service personnel have become far more accepting of homosexuality, suggesting that such a move could be less disruptive today than it would have been in the 1990s. At least 13,500 personnel have been discharged since 1994 over their sexual orientation, according to the Servicemembers Legal Defense Network, a nonprofit group working to repeal the ban.

A 2006 Zogby poll found that three-quarters of the military personnel surveyed said they were comfortable around gays and lesbians, while 78% said they would join the military even if gays were allowed to serve openly. Just under 25% of the respondents said they knew someone in their own unit who was gay.

Supporters of maintaining the regulation point to other polls which show more discomfort towards homosexuality within military ranks. A Military Times poll late last year found that 58% of the respondents opposed repealing the ban. Even within the Military Times poll, however, 71% of the respondents said they would continue to serve if the policy were repealed.

Mr. Obama, who spokes for about 25 minutes, told the crowd that he came to the gay community with a simple message: “I’m here with you in that fight….My commitment to you is unwavering.”

Introducing Mr. Obama, Human Rights Campaign President Joe Solmonese told the crowd, “We have never had a stronger ally in the White House. Never.”

Richard Socarides, who had advised the Clinton administration on gay and lesbian policy, told the Associated Press that Mr. Obama delivered “a strong speech in tone, although only vaguely reassuring in content.”

“The president and Nobel winner came and paid his respects, but tomorrow many will ask: What’s his plan, what’s his timetable,” Mr. Socarides said.

Other special interest groups that contributed to, and campaigned for, Mr. Obama, such as unions and Latino voters, have begun to question when he will address issues important to their members, such as legislation to facilitate union organizing at the workplace and an overhaul of immigration law.

Mr. Obama acknowledged some in the crowd believe that he hasn’t done enough so far to address issues facing the gay community. But he said, “Do not doubt the direction we are headed and the destination we will reach.”

“We have made progress and we will make more,” Mr. Obama said.

The president also referenced the House’s move this week to widen hate-crimes legislation and make it a federal crime to assault people based on their sexual orientation.

He offered a tribute to Matthew Shepard, a gay man who was tortured and killed 11 years ago in Wyoming because of his sexual orientation, igniting a nation-wide drive for expanded hate-crimes legislation. Mr. Shepard’s parents, Judy and Dennis, were on hand to accept the first Edward M. Kennedy National Leadership Award, presented by Rep. Patrick Kennedy (D., R.I.).

Mr. Obama said the administration was also addressing the continuing problem of HIV/AIDS. Guests at the $250-a-plate dinner included musical actor Gavin Creel, singer Lady Gaga and cast members of the television show Glee.