Reacting to a flurry of reports about the health of Soviet President Leonid I. Brezhnev and signs of political maneuvering in the Politburo, U.S. officials said yesterday that a transition of leadership clearly appears to be under way in the Soviet Union.

No comments are being made for the record, in keeping with the usual diplomatic practice between the superpowers. However, U.S. sources said reports from Moscow tend to confirm news accounts that the Soviet leader was hospitalized following a recent trip to Tashkent.

Officials said they are uncertain, however, whether Brezhnev's condition is very serious or whether, as some reports suggest, he has been hospitalized to regain his strength following exhaustion during his trip. There is no indication that Brezhnev is being treated as a terminal patient, sources said, and there are some indications that he is not.

The most definite fact, in the view of U.S. analysts, is the rise of a seemingly unconstrained Moscow rumor mill. Last week some of the rumors reaching Washington were that Brezhnev had died, an assertion that was not believed at the time and is not believed now. The important point, officials said, is not the inaccuracy of the various rumors but the fact of their unusually wide circulation.

Some of the rumors have concerned the ups and downs of Konstanin Chernenko, who is considered Brezhnev's closest associate and, to some, his emerging heir apparent. Other rumors dealt with the absence from the scene of Andrei Kirilenko, a Politburo veteran who is usually considered another contender for future leadership.

Chernenko is 70 years old, Kirilenko, 75--a few months older than Brezhnev.

Undersecretary of State Lawrence S. Eagleburger, answering questions from reporters last Tuesday, said the widespread rumors indicated "ferment, at least, which probably has to be put in the context of maneuvering for position." Eagleburger said "it's clear that there has been some hanky-panky, if you will, going on, and some people have been moved over others . . . . Clearly, there is something going on."

At the same time, he cautioned against reading too much into the maneuvering, and said he was not ready to conclude that a change in Soviet leadership is imminent.

In the opinion of some analysts, the death of veteran ideologist Mikhail Suslov Jan. 25 opened the floodgates of jockeying and speculation, and Brezhnev's poor health has added to the flow.

At high levels of the State Department, there is open skepticism about any suggestion that the United States could influence the Soviet succession process through its East-West actions. The next leader of the Kremlin, in this view, is likely to emerge through his own ability to fight his way to power in a rough internal political struggle.

While some hold that the next leader will be "the toughest guy in the pack," this is not believed to indicate much about his international political posture or his view of relations with the United States. Brezhnev, in an evaluation that seems to have a retrospective ring to it, is now being seen as, in some respects, more of a dove than a hawk in the international perspective.