After months of strenuously denying rumors that he was resigning, it appears likely that Teamsters President Frank Fitzsimmons is on the way out as head of the 2 million-member union.

The latest information from normally reliable sources in both the union and the government seems to indicate that the 69-year-old Fitzsimmons' possible retirement has been generated more by the political ambitions of his lieutenants and outside events than by any desire on the labor leader's part.

As pieced together from various sources, the prospects are these:

Fitzsimmons is due to resign by year-end, hoping that will avert possible government action against him, both criminal and civil, or his conceivable removal by a court as a result of corruption charges lodged against him last April by dissident union members. That scenario, of course, could be upset by unforeseen events, including a change of heart by Fitzsimmons, these sources say. But they emphasize that the current plan is for the president to step down soon. The sources also say that if Fitzsimmons isn't forced out by lear's end, legal pressure on him is becoming so irresistible that it seems clear he couldn't hang on much past the first of the year.

Replacing him as interim president, say these sources, will be Joseph Trerotola, 64, a mild-mannered Teamsters vice president from New York.

In the following six months, until a union-mandated convention takes place to elect a permanent president, a rivalry between two union leaders, Jackie Presser, 51, and Roy Lee Williams, 62, is expected to erupt into a bitter fight to determine who will control the huge union.

Though the smart money is gambling on Presser to end up on top, the selection of either won't stop the allegations that the Teamsters union is controlled by people connected with organized crime.

This scenario of Fitzsimmons stepping down supposedly was made final at a series of meetings among top officials of the union during a Fitzsimmons-sponsored golf tournament in mid-October at La Costa Country Club, the 6,000-acre resort in Southern California financed by $60 million in loans from the Teamsters Central States Pension Fund.

The background to all this is a long list of allegations over the years that Fitzsimmons used his union office to enrich himself and selected associates at the expense of the Teamster membership. Though none of the charges has ever been proven, they've nonetheless seriously tarnished the labor chief's image. Fitzsimmons and most other top union officials couldn't be reached because they were traveling after attending a Teamster retirement dinner in Dallas Wednesday night, but the Teamster president has vigorously denied the charges in the past.

Presser strongly denies that Fitzsimmons will retire, saying "there's absolutely no truth to those rumors. Fitzsimmons is going to finish out his full term, and the board is behind him 100 per cent." But two associates of Presser say his private comments are just the opposite: that Fitzsimmons is an ineffective leader and should be replaced, preferably by Presser. Ray Schoessling, another Teamsters vice president, echoes Presser's support for the Teamster chief.

The latest round of problems for Fitzsimmons begins next weeks when he will appear before the Senate Permanent Subcommittee on Investigation. That body is investigating Joseph Hauser, an insurance broker already convicted of bribing union officials to get their business. Senate investigators want to question Fitzsimmons about the award to Hauser of a $24 million-a-year Teamsters insurance contract that has since gone sour amid charges of fraud. According to information that has already surfaced, Fitzimons was partly responsible for former U.S. Attorney Genral Richard G. Kleindienst's receiving a $250,000 fee for helping Hauser land the contract.

The other serious item facing Fitzsimmons is a yet-unscheduled hearing within the next two weeks by the union's executive board, which has decided to hear formal charges filed by a group of dissidents that Fitzsimmons has misused his office and should be removed as an officer and member.

In addition, sources say the Labor Department task force investigating the Central States Pension Fund and its sister Health and Welfare Fund has turned up some evidence indicating Fitzsimmons may have been involved in some wrongdoing while he was a trustee of those funds.

A separate Labor Department investigating of the funds' procedures was dropped earlier this year in return for the resignations of Fitzsimmons and other trustees from their fund positions and other changes.

But although the current inquiry has gotten off to a slow start, federal officials haven't given any indication, public or private, that they would be willing to drop it in return for Fitzsimmons' resignation as Teamsters president.

Indeed, a key Labor Department aide familiar with the inquiry emphatically denied yesterday that any such deal has been offered by the government or proposed by the Teamsters. And this official further insisted that the idea would be rejected by the government if it ever arose.

However, sources speculated that members of the Teamsters leadership may believe such a tradeoff can be arranged, or may be trying to convinced Fitzsimmons of its likelihood, even though his departure from the union presidency wouldn't erase his possible legal liability for any past pension law violations the government may turn up.

If the Teamsters executive board finds any of the dissidents' charges true, some sources say, that could be grounds for Fitzsimmons' removal. On the other hand, if the allegations are rejected, the dissidents have already said they will go to court to try to have him replaced by a trustee. One union insider says board members see this as a "real possibility," citing the 1957 court-appointed Board of Monitors, which 13 dissident members forced on the union and which temporarily replaced James R. Hoffa as president.

Jackie Presser, the leading candidate to succeed Fitzsimmons, is the son of William Presser, long a Teamster leader and associate of organized crime figures. William Presser is still believed to be the most powerful figure in the Teamsters union by both union and government sources. He has lost two battles with the Justice Department, which has investigated him for about 20 years. In 1961, he was convicted of obstruction of justice and served six months in prison. Ten years later, he pleaded guilty to eight misdemeanor counts of shaking down employers on behalf of the union, but because of his health he avoided another jail term and instead was only fined by the court.

The younger Presser took over as a vice president when his father was forced to resign a similar post by government investigators earlier this year. Both men still hold several other Teamster posts in Ohio, their main power base.

Since taking the vice president's post, Presser has embarked on an extensive and visible campaign to be, come involved in the international's day-to-day affairs. He's most notably responsible for creating and directing a new union public relations effort in an attempt to add some luster to the Teamsters' tarnished image.

While the younger Presser hasn't been convicted or even charged with any crime, court testimony and several law enforcement agencies have linked him to meetings with organized crime figures.

Roy Lee Williams, director of the powerful Central Conference of Teamster, among his other positions, is probably right behind William Presser in union power and influence. Over the years, Williams has been indicted three times by the Justice Department, but he either has been acquitted or has had the charges thrown out. Currently, the Internal Revenue Service is focusing on William's role in an aborted prepaid legal plan promoted in 1973 by people with organized crime ties.