Saturday afternoon amid much music and marching and pageantry worthy of a halftime at the Orange Bowl, a ceremonial flame will be lit at Moscow's massive, 103-000-seat Lenin Central Stadium. This will mark the official opening of the final stages of a gigantic sports fesitval known officially as "the National Games of the People of the U.S.S.R.," and popularly as "Spartakiade."

Ordinarily, this would be an event of enormous interest within the sportloving Soviet Union, and of the minimal concern throughout the rest of the world. But this year, international attention is being paid to Spartakiade because it also signals the start of the countdown to the 1980 Summer Olympics in Moscow.

Precisely 354 days later, on July 20, 1980, the carrier of the fabled Olympic torch will enter the same Lenin Stadium -- centerpiece of the Lukzhniki sports complex on the banks of the muddy Moscow River -- and light the flame opening the 22nd Olympiad, the first held in a communist country.

The Spartakiade -- usually a competition among teams representing the various republic and diverse nationalities of the U.S.S.R. -- is being used this time partially as a dress rehearsal for the upcoming Olypmics which the Soviets are determined to use as a gaudy adverstisement for their nation and political system.

Accordingly, foreign athletes have been invited for the first time to compete been invited for the first time to compete and bronze medals in the final stages of the ongoing Spartakiade, a mass-participation extravaganza whose early stages include competitions in the schools, factories, farms and sports clubs of virtually every hamlet and city of this vast nation. Soviet officials say that more than 100 million people more than one-third of the nation's population took part.

More than 2,000 foreign athletes from 87 invited countries -- Israel, Chile, and nations such as New Zealand that maintain sports contracts with South Africa were conspicuously not invited by the Sport Committee of the U.S.S.R. -- will join the best Soviet athletes for the finals of 22 sports, including all those on the Summer Olympic program.

The theory was to give foreign athletes especially those who never have competed in the Soviet Union, a chance to "have the feel of the Moscow atmosphere," as U.S.S.R. sports czar Sergei Pavlov put it in a speech welcoming 700 foreign journalist to Spartakiade, as well as to provide officials an opportunity to road-test many facets of their Olympic organization.

However, as many skeptical Westerners are certain will be evidenced next year, Soviet theory often does not work out in practice.

Many fewer world-class athletes than originally expected decided that it was worth their while to come to Moscow a year in advance to get a sence of the peculiar hassles and psychological traumas of life here.

Suprisinly, East Germany and Cuba -- great socialist comrades of the U.S.S.R. -- decided that their best athletes would be better served by training and competing elsewhere.

The absence of such outstanding Cuban athletes as Alberto Juantorena, Silvio Leonard, Alejandro Casanas and Teofilo Stevenson, and East Germany's powerful women swimmers, apparently gave would-be rivals second thoughts about the value of competing at Spartkiade.

The American team of 16o athletes announced by the Amateur Athletic Union lost most of its most notable names at the 11th hour, including hurdlers Greg Foster and Edwin Moses, sprinter Evelyn Ashford, 400-meter whiz Willie Smith and middle-distance runners Mary Decker and Francie Larrieu.

Others, such as Steve Scott (800 meters) who was supposed to run Saturday were delayed by visa problems and listed as doubtful participants by Jimmy Carnes, the U.S. Olympic men's track and field coach and leader of the depleted U.S. track contingent for Spartakiade.

Tom Coulter, chief of the U.S. boxing

Tom Coulter, chief of the U.S. boxing team members were on the flight he took from New York to Moscow, but that. "We left 20 to 30 behind at the airport sitting on their bags, waiting for their visas to be issued . . . .I don't know if they will come or not."

All this follows the decision of several West European countries to send only token teams, and the withdrawal of all Norwegian athletes and journalists because one journalists was refused a visa by Soviet authorities.

The long list of noteworthy noshows certainly reduces the significance of the Spartakiade as an international competition, and virtually assures the dominance of Soviet athletes. But the event will remain interesting and important as a preview of what the world can expect from the Soviets as Olympic hosts.

Many sports, including track and field at the Lenin Stadium, are being played at the same venues that will be used for the olympics, and this affords athletes and coaches an opportunity to get used to the idiosyncracies of the facilities and their geographical relation to the Olympic Village and other Moscow landmarks.

"It's good to be in here now so we know what we can expect next year," said Carnes, who wll familiarize himself with bus routes, travel times and the physical layout of facilities so that he can advise the American team on such matters of vital detail next year.

The Spartakiade will also provide a valuable benchmark of Olympic readiness if not a full-scale dry run, for officials and support personnel for next year's Games.

There will be 3,500 referees and judges -- 'arbiters' as the Soviets call them -- working the Moscow Olympics 1,000 of them from abroad, and many of these have been invited with the sites and the equipment they will be using.

Officials will have a chance to try out recently built or refurbished facilities during Spartakiade as well as much of the complicated gadgetry -- complex electronic timers and score-boards computerized data transmittal ad communications systems, and the like -- that is an essential part of the modern mega-Olympics.

The Soviet's network Gosteleradio -- which stand for "Government Television and Radio" -- will televise between five and six hours a day of Spartakade over the next two weeks, using the same caremamen, directos and technicians who will originate the "international feed" of next year's Olympics.

This experience will enable them to sharpen their techiniques, and will also give the foreign TV executives and production personnel -- who are here in force -- an occasion to observe the Soviets in action and evaluate their performance.

Even though Spartakiade is run by the U.S.S.R. Sports Committee and not the Olympic Organizing Committee it will give the Olympic organizers and sports authorities at the Kremlin a small taste of what it will be like to house, feed, transport and impress the thousands of athletes, VIP's journalists ad tourists who will come to Moscow for theOlympics.

The 7,500 journalists, 2,000-odd invited guests, and half a million spectators expected for the Olympic Games will comprise the biggest "invasion" of foreigners the Soviet Union has ever known, and the Big Brothers of the Kremlin want them and the billion-plus people who will watch the Olympics on television around the world to be favorably impressed with Soviets technology and hospitality.

Not since 1936, when Hitler tried to use the Berlin Oplympics an international demonstration of the superiority of Nazi Germany and the Aryan race has a sporting even been so decidely geared toward presenting a facade of political accomplishment.

In Russian, the word for it is "pokazuha" -- meaning, for show" The Soviets want to show the world, through the Olympics, that their society is technologically advanced, prosperous and classless -- even if it is none of those things.

That is why they have halted virtually all nonOlympic contruction -- housin, hospitals, everything -- until all the Olympic facilities are completed. That is why they have stock-piled food to serve to foreign guests while citizens outside of Moscow cannot buy meat. That is why they have spent untold energy training waiters and taxi drivers and hotel employes to treat Western guests to better service than has ever been the the case here before.

That is why thousands of youths from sports clubs were our rehearsing colorful opening ceremonies at Lenin Stadium this week -- and Soviets are acknowledge masters of pomp and ceremony -- and why workmen were painting the green frnces around contruction sites at Luzhniki this morning in a pouring rain: The Soviets do things "poplanu" -- "according to plan" -- and if it happens to rain on a painting day, they paint on.

And that is why the 700 foreign journalists here will pay careful attention to Spartakiade the next two weeks even if the competition is not up to the hope-for standard. This is the dress rehearsal for an Olympics that raises provocative questions beyond the realm of pure sports competition, and it will provide clues to how the Moscow Olympics will work out, even if few indications of who will win the medals.