Thousands of homesexuals from across the country are expected to converge on Washington this weekened for three days of events that will be highlighted Sunday by the first national gay rights march.

Although march organizers have estimated that 100,000 homosexuals will attend, bickering among march leaders and indifference by some national and local groups are expected to reduce that number. Based on projections by Washington's homesexual leaders, local police said they expect far fewer than 100,000.

At the same time Sunday as the march, a Christian religious coalition, including the Rev. Jerry Falwell of Lynchburg, Va., and antigay activist Anita Bryant will hold a press conference and prayer service in the Rayburn House Office Building to oppose the march and its goals.

The purpose of the march, besides giving homosexuals national visibility, is to support the idea of congressional legislation to prohibit discrimination based on sexual preference. Organizers also hope to persuade President Carter to sign an executive order banning sexual preference discrimination in the military and within the federal government. They also hope to end what they say in discrimination against homosexual parents in child custody cases.

Throughout the weekend, activist groups will hold caucuses to explore ways to advance gay rights.

The weekend's activities include a three-day Third World Conference of Lesbians and Gays at the Harambee House hotel to discuss concerns of minority homosexuals, including Indians, black,s Chicanos and Asians, and the second annual Law and the Fight for Lesbian and Gay Rights Conference Saturday evening at George Washington University's Marvin Center. The Washington area Women's Center will hold a women's dance in the Blue Room of the Shoreham Americana Hotel.

D.C. Mayor Marion Barry has proclaimed Oct. 10-17 as Gay Rights Awareness week. Barry will speak at the Third World Conference of Lesbians and Gays and is one of the scheduled speakers for the rally after Sunday's march.

Marchers will gather near the Capitol at noon for a march down Pennsylvania Avenue, then the group will turn south at 15th Street NW for a rally at the Monument grounds about 2 p.m.

Speakers will include Lucia Valeska, coexecutive director of the National Gay Task Force; Eleanor Smeal, president of the National Organization for Women; Harry Britt, San Francisco City supervisor, and Betty Santoro, New York spokeswoman for Lesbian Feminism Liberation.

At the same time, religious activist groups will hold a press conference in Room 2325 of the Rayburn House Office Building to protest the homosexual campaign. They will also hold a prayer service at 2:30 p.m. after the press conference in Room 2318 of the same building.

"We thought it was important that there was a viewpoint from the Christian community on all this," said Gary Jarmin, a spokesman for the groups. "We don't intent to make this a campaign of persecution of homosexuals, but to pray for their repentance.

"We feel that homosexuals are becoming increasingly militant and aggressive, trying to force the country to accept their life styles as legitimate. We don't believe it is," Jarmin said.

Although the Washington homosexual community has responded to the march half-heartedly because many of tis leaders oppose its timing, that community is gearing up for the thousands who will be here.

Jim McCollam, manager of the gay bars Lost and Found and the Pier, said he has added about 10 workers for each bar each weekend night and has "substantially increased" his liquor stock and doubled his beer orders.

March spokesman Brandy Moore said Washington homosexuals have also opened their doors to marchers needing places to stay, and 2,000 people have signed up as marshals for the march.

For several years, Washington's homosexual groups have been successful in their gay rights agenda, effectively lobbying the city government to secure legislation barring discrimination against gays, and enjoying through political power the attention of the mayor and most of the City Council. Homosexuals have established joint committees with the police department, elected overtly gay people to the city's Democratic State Committee, and have succeeded in having homosexuals appointed to city commissions.

Some local homosexual leaders expressed concern about the march leadership -- a new group of gay activists -- and their ability to conduct a march of the magnitude planned. They have been critical of some of the march's top leaders, who local leaders say represent more lefist views of gay activism rather than the mainstream homosexual community.

"It should have been a clue to a lot of people that the national and local organizations did not give immediate endorsement," said Bod Davis, former president of the local Gay Activist Alliance, which endorsed the march with reservations.