By Edith Honan

NEW YORK (Reuters) - New York mayoral candidate Bill Thompson was resisting pressure from fellow Democrats on Thursday to bow out of the race in favor of front runner Bill de Blasio and avoid a bruising run-off, campaign aides said.

De Blasio, the city's public advocate, won by far the most votes in the intrigue-filled Democratic primary to follow Mayor Michael Bloomberg into City Hall, but many ballots were still to be counted and it was not yet clear he could avoid an October 1 run-off race with Thompson, potentially damaging the Democrats.

The winner will face Republican Joe Lhota, a deputy mayor under former Mayor Rudy Giuliani, on November 5 for the top job in the biggest U.S. city.

Thompson was reluctant to throw in the towel before the final vote was tallied, possibly not before next week, aides said, but a meeting with labor unions and prominent black politicians later on Thursday could force his hand.

"It's important that every voice be heard and every vote be counted. That's the number one priority," said spokesman John Collins. He said the final vote count is expected to continue through next Tuesday or Wednesday.

Thompson, who has no public events scheduled for Thursday, will hold a closed-door meeting with key supporters later in Wednesday, including Congressmen Charles Rangel, an influential Harlem Democrat, and representatives from the United Federation of Teachers, his campaign said.

"I see no value coming out of a battle of two Democrats," said George Gresham, the president of the 1199 SEIU, the health care workers union that endorsed de Blasio during the primary.

Gresham said that he and others in the union were reaching out to Thompson and key backers to urge the candidate to exit the race.

Even his campaign seemed divided, with senior officials such as chairwoman Merryl Tisch indicating it was time for Thompson to bow out.

"He'll decide what he wants to do when he's ready," said Hank Sheinkopf, the Democratic consultant who advised Thompson's campaign. "He's always strong-headed. He always makes his own decisions."

DEMOCRATS RALLY AROUND DE BLASIO

At a rally at Brooklyn Borough Hall, de Blasio made no mention of Thompson and behaved like his general election campaign against Lhota had already begun.

"It's time to stare in the face this tale of two cities and it's time to end it," de Blasio said to chants of "Go! Go! De Blas-i-o!"

Several major unions that had endorsed City Council Speaker Christine Quinn, the mayoral race's third-place finisher, said they would switch their support to de Blasio.

De Blasio, the public advocate, built his campaign around addressing income inequality, and has called for higher taxes on the rich to pay for expanded pre-kindergarten, more affordable housing, and reform to the police tactic of stop and frisk.

That message, as well as the prominent role played in the campaign by his charismatic, mixed-race family, contributed to de Blasio's strong finish in the primary against six other candidates, almost winning outright with 40 percent of the vote.

The fact that de Blasio, who is white, won a majority of the black vote was seen as a major blow to Thompson, who was running to be the second black mayor in city history and got 26 percent.

"We're talking about 40 versus 26," said City Councilman Jumaane Williams, who endorsed de Blasio and is now urging Thompson to drop out. "It's not a really sympathetic argument."

The Board of Elections said if one of the two top vote getters drops out, the other would automatically be declared the primary's winner.

(Reporting by Edith Honan)