The biathlon, a contest of cross-country skiing and riflery, prides itself on its Olympic spirit. Competing teams train together and share techniques with little regard for nationalism.

Despite the camaraderie and international assistance, however, the United States' chance of winning a medal is slight. The U.S. competitors never have lived up to their potential, and the question is whether they can stand up to the pressures of the Olympics.

One problem facing the U.S. team is that the field from which the Olympic biathlon competitors are chosen is so small. There are fewer than 300 Class A competitors in the U.S. By comparison, there are 50,000 Class A competitors in the U.S.S.R. and 10,000 each in Finland, Sweden and Norway.

Biathlon is a paramilitary sport, introduced to the Olympics in 1960. Competitors ski cross-country loops and stop to fire five shots from a small-bore .22 caliber rimfire rifle at a target 50 meters away. Missed shots mean penalties that add to a racer's total time.

Biathlon events include the 20-kilometer (12.5 mile) race, a 10-kilometer race and a four-man 30-kilometer relay.

There are no standing records in the biathlon because of the difficulty equating courses and snow conditions. The Soviet Union's Alexander Tichonov is the world's outstanding biathlon competitor, an 11-time world champion.

Top U.S. competitors include Don Nielson, 28, of South Strafford, Vt., and Lyle Nelson, 32, of McCall, Idaho. In the 1976 Olympics Nelson had the second-fastest time on the first leg of the relay, although the other racers did not maintain Nelson's pace.

Nielson had a near win in Steamboat Springs, Colo., in March this year at the Dannon Yogurt relays which pit the U.S. racers against a Canadian team. According to Peter Lahdenpera, vice president of biathlon on the U.S. Modern Pentathlon and Biathlon Association, and a member of the U.S. biathlon team, Nielson would have won "if he had been racing to his potential."

Lahdenpera thinks either Nielson or Nelson stands a good chance of winning if the snow conditions are favorable and the racers are primed.

The American team trained this year with the Soviet Union's Tichonov, and with Heikki Ikola, a medalist and world champion from Finland, who was brought to the U.S. twice during training camps. The team also worked with the Norwegians when they were in Europe.

Training is on snow as much as possible . Although no on-snow camps are scheduled for the summer, an early training camp is planned in October in Europe.

During the summer the team runs and uses roller skis, which are cross-country skis set on polyvinyl rollers. (Two team members were stopped by state police in Colorado last summer for using the roller skis on state highways; one got away with a warning, but the other was socked with a $25 fine. The state police have agreed not to ticket biathloners this year.

Biathlon supporters point out that this sport is far more widespread than Nordic skiing, even though many Americans think a biathlon is some kind of indoor sauna.

In the 1978 world championships 18 countries fielded Nordic skiing teams, but 30 countries were represented in the biathlon.

The international favorites for next year's Olympics include Frank Ullrich and Kalus Siebert, both former world champions from East Germany; Heikki Ikola of Finland; Odd Lirhus of Norway, a former world champion, and Vladimir Alikin and Tichonov of the Soviet Union.

Although the paramilitary nature of the sport has so far precluded women from competing, by next year Norway, Finland and the Soviet Union are expected to field women's teams. While the United States has allowed a few women to train with the team at Squaw Valley this year, the decision has not been made to start women's competition in the Olympics.