An influential Queens minister and former Democratic congressman publicly endorsed Mayor Bloomberg for reelection yesterday and said he expected to stump actively for the mayor as the campaign season gets under way.

In the first major political endorsement of the 2005 mayoral campaign, Rev. Floyd Flake, senior pastor at the 15,000-member Allen A.M.E. Church in Jamaica, made good on news reports from last week that he would back Mr. Bloomberg.

Mr. Flake introduced the Republican-turned-Democrat to the African-American congregation and then appeared with him immediately after the service at an assisted-living center a few blocks away to make his endorsement official.

Mr. Bloomberg sat in the front pew of the two-story cathedral with one of his deputy mayors, Dennis Walcott, who is African-American, as Mr. Flake delivered a fiery sermon and the choir had the crowd dancing and singing.

The mayor, who is Jewish, told the congregation that the city was “going in the right direction” and that crime was down in Jamaica by 20%. He also touted his overhaul of the city’s public school system and said his plan to abolish “social promotion” of students to the next grade would provide children with a better education. “There are an awful lot of things go ing right in this city, but we do have a long ways to go, and what we’ve got to do is stay the course,” the mayor told the congregation. “Sometimes it isn’t easy, and sometimes you take two steps forward and one step back.”

The pastor, a key figure in the Queens African-American community, lauded Mr. Bloomberg for his education reforms, his affordable-housing initiative, his handling of the post-September 11 recession, and his commitment to the minority communities.

The endorsement is a significant one for the mayor, who like his Democratic opponent in the general election next November will need a healthy share of the African-American vote to win City Hall. It is also likely to be the first of several endorsements of him from conservative Democrats, whose support is expected to be crucial in a city where Democrats outnumber Republicans by a five-to-one ratio among enrolled voters. Some Democrats on the City Council, including Madeline Provenzano of the Bronx, are also expected to back the Republican mayor. Ms. Provenzano told The New York Sun last week that she had not yet been asked for her endorsement but would gladly deliver when the mayor’s office calls.

Mr. Flake endorsed a Democrat, Mark Green, over Mr. Bloomberg in the 2001 election and Mayor Giuliani, a Republican seeking his second term, in 1997. Before that, however, he endorsed Mayors Dinkins and Koch, both fellow-Democrats.

“I don’t think that anyone who will enter this race or is in this race has the ability to see the economic realities of this city better than the mayor who stands beside me today,” Mr. Flake told a group of senior citizens in a lounge at the Allen Community Senior Citizen Center.

“He has not been one to call press conferences based on what he has done for people of color or any other people,” Mr. Flake continued. “He has been a mayor for all of the people of New York.”

Mr. Bloomberg, who used the short time after both events to shake hands and mingle, was met mostly with positive reviews. While most said they respected Mr. Flake, they also said they would ultimately make their decisions based on things like subway fares, property taxes, and schools.