The Queens County Republican Party will endorse the former GOP leader of the City Council, Thomas Ognibene, for mayor next month, strengthening a campaign that could threaten Mayor Bloomberg’s chances of winning re-election, The New York Sun has been told.

The Queens party chairman, State Senator Serphin Maltese, did not return phone calls from the Sun yesterday, but Mr. Ognibene, who is vice chairman of the county GOP, confirmed in a telephone interview that the party organization had agreed to give him the endorsement at a meeting scheduled for February 10.

“This is important. The largest Republican vote comes out of that borough,” a Baruch College professor of political science, Douglas Muzzio, said. “Is it a surprise? No. Is it meaningful? Absolutely.”

Mr. Ognibene said the formal kickoff of his campaign for mayor will come soon after the Queens County nod. “I’ll do it at a different event from the endorsement,” he said. “But it will be an event soon after February 10.”

The prospect of the support in his home borough adds momentum to the Ognibene campaign, particularly because it should translate into help circulating petitions to get the challenger’s name on the ballot for the primary.

In a related development, the mayor commented yesterday on reports that his re-election campaign offered the former city council member a $12,000-a-month job. There have been suggestions the offer was a bid to keep Mr. Ognibene from challenging Mr. Bloomberg in a Republican primary. Mr. Bloomberg said he didn’t know Mr. Ognibene was running when his operatives approached the Queens Republican.

“Tom Ognibene was someone who supported me four years ago,” Mr. Bloomberg told reporters in Staten Island yesterday. “It was our understanding that he was not running for mayor. I think my campaign did approach him to see if he would want to become involved in the campaign. Two days later, we read in the paper that he was running, and we had no further contact with him.”

In an interview with the Sun yesterday, Mr. Ognibene said: “I said no to the job because I’m not for sale.”

While he said he didn’t find the job offer untoward, he was concerned when a Bloomberg campaign aide suggested that if he ran for mayor, questions about his role in a bribery investigation involving the city’s buildings department in the 1990s would resurface.

“The aide told me that if I thought that was over, it wasn’t,” Mr. Ognibene said. He was never charged with a crime in that investigation.

While political analysts – and even Mr. Ognibene – doubt he can be elected mayor in a town where registered Democrats outnumber Republicans by five to one, the former council member is considered a formidable opponent who could end up as a spoiler. If enough of the city’s half-million registered Republicans decide to exact revenge for Mr. Bloomberg’s property-tax hike or his smoking ban, for example, then Mr. Ognibene could win the primary.

Mr. Ognibene said he has yet to start raising money for his bid but expects to qualify for the 6-to-1 match in public campaign subsidies for which candidates who are up against big-money rivals, like Mr. Bloomberg, can qualify. Mr. Ognibene said he expects to raise enough money to hit the $250,000 threshold, which would give him more than $1 million with which to compete against the mayor.

Mr. Ognibene rose through the ranks of the state’s Conservative Party to become a Republican insider in the Giuliani administration. He represented a working-class area of Queens, known as the “Archie Bunker district,” for a decade in the City Council, and he was able to convince many Democrats in his district to keep voting for him.

A third Republican plans to run for mayor in this year’s primary, Steven Shaw, an investment banker.

In 2001, Mr. Bloomberg easily defeated Herman Badillo in the Republican primary. Then as now, even if he lost a Republican primary, he could run in November on the Independence Party line.

In the general election four years ago, two-thirds of Mr. Bloomberg’s 78,040-vote margin of victory came from Queens.