Moscow — Blue jeans have given way to Bjorn Borg togs as a Moscow status symbol, just one sign that a minor tennis boom has hit the Soviet Union. More important to the nation's small - and in recent years, frustratingly homebound - band of top players, even the Kremlin may be taking a new shine to the lob, the slice backhand, and the good old topspin put-away.
One reason: Tennis, after a decades-long interlude, is being reinstated as an Olympic sport. Doing well at the Olympics is as Soviet as apple pie is American.
Problems remain: The number of tennis courts in some cities has dropped in the past decade. Soviet rackets and strings - a Moscow newspaper lamented last year - are of depressingly poor quality. So, the paper assumed, were Soviet tennis balls, but it added il7l,0,10l,5pacridly, ''They are so scarce it is hard to say anything about their quality.''
Nowhere near as many youngsters play tennis as in even smaller Western states like France - although the Moscow elite has visibly begun to succumb to the West's renewed mania for the sport. In all, as of last year, there were only an estimated 41,000 Soviet players nationwide.
The rebirth of official interest in tennis has been some time coming: In the 1960s and early '70s, two Soviet players - Georgian Alex Metrevelli and Russian Olga Morozova - played the world tour and did quite well. Metrevelli even made the finals at Wimbledon, albeit in 1973, when top players boycotted in a spat with tournament organizers.
But as interest in tennis exploded worldwide, and as the competitive level soared, Soviet players suddenly cut back to only occasional trips abroad.
Mrs. Morozova, now national Soviet women's coach, attributes this to the fact that in a sport where youth increasingly dominates, young Soviet prospects, as amateurs, can't simply pick up and follow the world tour. ''People like (Czech star Ivan) Lendl are pros. . . .''
Some players privately offer another possible explanation: jitters on high that the glitter of the tour might tempt players to defect.
Whichever, Mrs. Morozova says that, particularly with the world system of competitive points for tournament ranking and qualification, a player who doesn't play the circuit is at an automatic disadvantage. She and others in the tennis establishment sense a recent increase in official interest in the sport, although this is still nowhere near on a par with local supersports like ice hockey.
Mrs. Morozova predicts that Soviet tennis players, including the youngsters she sees as her nation's tennis hope for the future, will gradually begin traveling more.
Two highly touted youths are 15-year-old Georgian Volodya Gabrichidze, a Metrevelli protege, and 16-year-old Larisa Savchenko. Savchenko is vying in the junior division of Wimbledon this year.
The two most visible Soviet men's players of late - though losers in a Moscow contest in March with a strong French Davis Cup team - are veterans Konstantin Pugayev and Vadim Borisov.
Borisov even beat a much rawer Yannick Noah in a Soviet-French Davis Cup tussle in the early 1970s. Pugayev has a devastating serve-and-volley game.
But other players say neither man is really up to top world class. ''What's their incentive, or their prospects, if they don't tour with really top players in the West?'' a player asks.
The Soviet newspaper Literary Gazette, in an attack last fall on the state of Soviet tennis, said much the same, explaining: ''Only those who play against strong opponents about 200 days a year can achieve outstanding suc-cesses. . . .''
''The solution is to provide better competition, build better courts, produce high-quality rackets, balls, and strings,'' the paper said.
''Tennis is a very prestigious sport that is making rapid progress on all continents,'' the article concluded. ''And it does not befit us, with our brilliant achievements in many types of sports, to lag behind.''