WASHINGTON - Thousands of gay and lesbian activists marched Sunday from the White House to the Capitol, demanding that President Barack Obama keep his promises to allow gays to serve openly in the military and work to end discrimination against gays.

Rainbow flags and homemade signs dotted the crowds filling Pennsylvania Avenue in front of the White House as people chanted "Hey, Obama, let mama marry mama" and "We're out, we're proud, we won't back down." Many children were also among the protesters. A few counter-protesters also joined the crowd, which stretched several blocks by the afternoon.

Jason Yanowitz, a 37-year-old computer programmer from Chicago, held his daughter, 5-year-old Amira, on his shoulders. His partner, Annie, had their 2-year-old son, Isiah, in a stroller. Yanowitz said more straight people were turning out to show their support for gay rights.

"If somebody doesn't have equal rights, then none of us are free," he said.

"For all I know, she's gay or he's gay," he added, pointing to his children.

Some participants in the National Equality March woke up energized by Obama's blunt pledge to end the ban on gays serving openly in the military during a speech to the largest gay rights group in the U.S. Saturday night.

"I will end 'don't ask-don't tell,"' Obama said Saturday night to a standing ovation from the crowd of about 3,000 at the annual dinner of the Human Rights Campaign.

He offered no timetable or specifics on changing the so-called "don't ask, don't tell" policy, which allows gay men and women to serve as long as they keep their sexual orientation hidden, and he acknowledged some may be growing impatient.

The chairman of the Senate Armed Services Committee said Sunday that Congress will need to muster the resolve to change the "don't ask, don't tell policy" -- a change that the military may be ready for.

"I think it has to be done in the right way, which is to get a buy-in from the military, which I think is now possible," said Sen. Carl Levin, a Michigan Democrat.

In his Saturday night speech, Obama also called on Congress to repeal the Defence Of Marriage Act, which limits how state, local and federal bodies can recognize partnerships and determine benefits. He also called for a law to extend benefits to domestic partners.

He expressed strong support for the HRC agenda of ending discrimination against gays, lesbians, bisexuals and transgender people but stopped short of laying out a detailed plan for how to get there.

Obama's political energies have been focused on two wars, the economic crisis and health care reform, though he pledged "unwavering" commitment even as he wrestled with those problems.

March organizer Cleve Jones, creator of the AIDS Memorial Quilt and a protege of slain gay rights pioneer Harvey Milk, said he had initially discouraged a rally earlier in the year. But he and others began to worry Obama was backing away from his campaign promises.

"Since we've seen that so many times before, I didn't want it to happen again," he said. "We're not settling. There's no such thing as a fraction of equality."

Jones noted that the debate over how to achieve progress has at times been bitter, but said people should look to the civil rights debates of 1963.

"There should be heat. There should be controversy because ... we're trying to change the strategy" to pursue full equality rather than a piecemeal approach, he said.

Organizers were expecting at least 75 busloads of people for the march at noon (1600 GMT) near the White House. Unlike the first march in 1979 and others in 1987, 1993 and 2000 that included celebrity performances and drew as many as 500,000 people, Sunday's event was driven by grassroots efforts and was expected to be more low-key.

Many organizers were outraged after the passage of California's Proposition 8, which cancelled the right of gays to get married in the state, and over perceived slights by the Obama administration.

Kipp Williams, a 27-year-old San Francisco resident, said he moved to California from the South seeking equality but realized after Proposition 8 that gay people are second-class citizens everywhere.

Sara Schoonover-Martin, 34, came from Martinsburg, West Virginia, with her wife, Nicki, wearing matching veils and pink T-shirts that said "bride" and "I do." The couple eloped at Martha's Vineyard in Massachusetts -- where gay marriage is legal -- earlier this year.

"When marriage is legalized in West Virginia, we will renew our vows and have our family and friends there," Sara said. "I'm angry that it hasn't occurred quicker. This affects my life every day, 365 days a year."

For Lt. Dan Choi, the day began with a jog around Washington's memorials, calling cadence at 8 a.m. with fellow veterans and supporters before joining the march. Choi, a West Point graduate, Arabic speaker and Iraq war veteran, is facing discharge under the military's "don't ask, don't tell" policy for revealing in March that he is gay.

He appeared later at a rally, wearing his Army uniform and a piece of black tape over his mouth.

"Many of us have been discharged from the service because we told the truth," he said. "But I know that love is worth it."

Other activists doubted the march would accomplish much. They said the time and money would have been better spent working to persuade voters in Maine and Washington state to support gay rights.

In Maine, voters will decide whether or not to uphold the state's legalization of same-sex marriage. In Washington state, a so-called "everything but marriage" law that expands the state's current domestic partnership law will be on the ballot.

A bill legalizing same-sex marriage in the U.S. capital also was introduced last week by the District of Columbia Council and is expected to easily pass.