Soviet Foreign Minister Andrei Gromyko, for more than 40 years an important player in Soviet diplomacy, is now one of the inner circle of men who dominate the Kremlin's political hierarchy and make its important decisions.

His steadfast, unobtrusive loyalty and reputation as a tough negotiator have been recognized by a succession of Soviet leaders. But in recent years, as poor health blurred the authority first of Leonid Brezhnev, Yuri Andropov, and then Konstantin Chernenko, Gromyko's stature in the Kremlin collective leadership has grown even greater. His knowledge of world leaders, which perhaps no other foreign minister could match, has made him indispensable.

At 75, Gromyko also is the healthiest of the Politburo's old guard.

A career diplomat with no political power base of his own, Gromyko never has been seen as a contender for the top job, and on domestic issues, his opinion probably carries no more weight than others in the Politburo. But in the absence of a strong leader, Gromyko's personal prestige, skill and experience appear to have earned him the leading role in the international realm.

Gromyko, who has been foreign minister since 1957, was named to the Politburo in 1973 and made a first deputy premier in 1983. He has dealt with nine American presidents, 14 secretaries of state and six Soviet leaders.

His grasp of international politics is impressive and his memory prodigious. Western officials who have dealt with Gromyko say he is tough, shrewd and cynical, and committed to a hard-line defense of Soviet interests. Gromyko, as the chief spokesman of a Soviet line that has put the blame for the breakdown in arms control talks on the U.S. administration, would be key in any decision to lower the level of rhetoric from Moscow.

Born into a poor Byelorussian peasant family on July 18, 1909, Gromyko is invariably urbane and sophisticated, even when feigning anger.

As the man in charge of foreign policy for more than a quarter of a century, Gromyko helped draft the United Nations charter while Ronald Reagan was still pursuing his Hollywood career and Margaret Thatcher was an Oxford undergraduate.