Fairfax County Executive J. Hamilton Lambert, one of the region's most widely known and respected local government officials, has submitted a letter to the Board of Supervisors indicating that he intends to resign at the end of the year.

Several supervisors said yesterday that it is unclear whether Lambert really plans to end a 10-year tenure in which he has been the driving force behind the Washington region's largest local government. They speculated that the letter may be an attempt to protect certain benefits or a tool for negotiating a new contract.

As county executive, Lambert has mediated regional squabbles, amassed extraordinary power and outlasted all his peers in the Washington area, winning a reputation as the "dean of the Beltway bureaucrats."

He helped negotiate regional water, sewer and garbage agreements and is involved in negotiations for a regional jail site.

Lambert has been mentioned recently as a possible candidate for the post of general manager of Metro or executive director of the Metropolitan Washington Council of Governments. Metro's current general manager, Carmen E. Turner, is leaving in mid-December for a high-ranking job at the Smithsonian Institution, and COG Executive Director Walter A. Scheiber has announced he will retire in January.

"It's not {Lambert's} intention to retire and it's not our intention to let him do that," said Supervisor Joseph Alexander (D-Lee), who as chairman of the board's personnel subcommittee was authorized by the board on Monday to open discussions with Lambert about continuing in his job.

Lambert is eligible to retire Nov. 18, on his 50th birthday, with an annual pension of about $100,000. However, close associates say they do not believe that Lambert really wants to quit after 31 years of service in the county government. Rather, they said, he is angry that the board has not approached him about his plans despite strong indications that he was thinking of resigning.

Lambert declined to comment on the matter yesterday. In recent months, he has told confidants that he is considering retiring from county government for a variety of reasons, including declining health, the strain of working for a fractious board, public attacks on his character and calls for his resignation. He also has been said to be reviewing other job opportunities and financial considerations.

Lambert started with the county in 1959 as an assistant map draftsman, and rose rapidly through the ranks to become the chief administrative officer in 1980. He oversees a $2.3 billion annual budget and more than 10,000 employees.

He was offered a state cabinet post by former governor Gerald L. Baliles and frequently makes trips to Richmond, where he is held in high regard by state lawmakers, particularly for his fiscal and political acumen.

Lambert's retirement letter, given to Alexander last Wednesday, essentially forces the Board of Supervisors to the negotiating table.

It is unclear what it might take to keep Lambert on the job, or what the board might be prepared to offer him.

With county residents complaining more and more about tax increases and exorbitant government spending, a significant salary increase or enhanced pension package for Lambert could be a tough political decision for the supervisors with elections just a year away.

Lambert got a 3 percent pay raise in June -- the same as all other county employees -- boosting his annual salary to $129,348 and keeping him as one of the highest paid local government employees in the country. The board's two Republican supervisors -- Thomas M. Davis III (Mason) and Elaine N. McConnell (Springfield) -- voted against the salary increase, saying government employees in general -- and Lambert in particular -- were paid enough.

"J is a very, very capable administrator, and it would be a tremendous loss to the county to have him go, especially with so much on our plate and a year before elections. It would be very disruptive," said Supervisor Sharon Bulova (D-Annandale), chairman of the board's budget subcommittee.

"J is also a very smart man, and he's sensitive to our budget situation right now, so I would think he'd be reasonable with what he'd expect or what he might ask for."

Both Davis and McConnell said yesterday that they hoped Lambert would stay on at least until the next board takes office after elections in November 1991. Davis said he viewed Lambert's retirement letter as "a formality. He has to do that or lose his opportunity to take leave and that sort of thing."

According to Lambert's contract, he could forfeit a certain amount of pay for accrued leave if he were to leave after Dec. 31 or not give the board 60 days' notice of his intention to retire.

According to Alexander, Lambert therefore had to submit his retirement letter by Nov. 1 or risk losing a potential lump-sum payment of as much as $30,000 when he retires.

"I don't know what the price is" to keep Lambert, Davis said. "It's not unlimited, of course . . . . If he wants that $30,000 when he leaves a year from now, that doesn't seem unreasonable to me at first blush."

McConnell agreed that such an arrangement "wouldn't give me heartburn," adding, "It would be a disaster to leave the county in the hands of {Board Chairman} Audrey Moore."

Moore could not be reached for comment yesterday.