INDIANAPOLIS, AUG. 20 -- It was another evening of mixed success for the U.S. boxing team at the Pan American Games. Success against some people, but not the Cubans.

Bantamweight Michael Collins of LaPorte, Tex., and welterweight Todd Foster of Great Falls, Mont., tonight became the fourth and fifth U.S. fighters to advance to the gold-medal finals, each with unanimous decisions in semifinal bouts. Collins clinched at least a silver medal with a 5-0 decision over Puerto Rico's Rafael DelValle, and Foster ensured one also as he defeated Wanderly Oliveria of Brazil. Both will meet Cubans in the finals on Saturday.

But two more Americans lost in the semifinals, once again to Cuba, in 5-0 unanimous decisions that made the United States 2-7 in nine meetings with its nemesis. Frank Liles of Syracuse was defeated by defending Pan Am champion Orestes Solano at light middleweight, and Michael Bent of Queens, N.Y., fell to brilliant young heavyweight Felix Savon.

Cuba will send 10 of a possible 12 boxers to gold medal bouts Saturday and Sunday. The United States sends five, with three of the Americans meeting Cubans for gold.

"My thoughts are that it was a success to some extent," said U.S. Coach Roosevelt Sanders said. "We didn't completely do what we wanted to do."

Sanders had hoped to place seven Americans in gold-medal bouts. He was two short in his estimate. Instead, Liles and Bent will take home bronze medals.

"We're 2-7 and that's not a good record against anyone," Bent said.

But those who won tonight did it decisively, and are given good chances in the finals. Collins defeated DelValle with a careful bout in which he took all three rounds conclusively. Then he said, "I think I won the medal tonight."

Saturday, he meets Cuba's Manuel Martinez, who also advanced tonight, with a unanimous decision over Domingo Damigella of Argentina.

"I've been waiting for this all week," Collins said. "If I'm not ready now, I'll never be."

Foster's unanimous decison was equally as decisive. The Olympic Festival champion was rarely troubled by Oliveria, the South American champion. But that won't be the case when he meets Cuba's Candelario Duvergel in the finals Sunday. The reigning Pan Am champion, he is regarded as the class of the Cubans, and stopped Daniel Gueto of Panama just 2:58 into the first round tonight.

In other gold medal bouts involving U.S. boxers, Michael Carbajal of Phoenix meets Luis Rolon of Puerto Rico at bantamweight, and featherweight world champion Kelcie Banks meets Emilio Villegas of the Dominican Republic. Both have already dispatched Cuban opponents. Also on Saturday, world champion Kenneth Gould meets knockout artist Juan Lemus in a welterweight bout that will be the third of the U.S.-Cuba confrontations for a gold medal.

The United States could take partial consolation in the knowledge that two of its losses involved injuries. Andrew Maynard, after winning the first round, had to retire against light heavyweight Pablo Romero because of a sprained right foot, and super heavyweight Riddick Bowe had a sore right hand in a narrow 3-2 decision to Jorge Gonzales.

Bowe said he had a fracture, but X-rays did not show it; however, U.S. team physician William Grana said a stress fracture might be undetectable.

Maynard said in an interview earlier in the evening that he went into the bout with the ankle already injured. He said he twisted it while he was playing basketball alone after a run, and had concealed it from Sanders.

Sanders had banned Maynard from the basketball court when the team arrived because the light heavyweight has a habit of injuring himself before big fights. Maynard said he tried to move around as little as possible before the Romero fight, and tied his shoes as tightly as possible to conceal the injury in sparring sessions.

Maynard said he was confident that even with the injury, he was was beating Romero. When he fell, he said he simply lost his balance on the sore ankle while trying to chase Romero with a hooking right.

"I can tell you this, I was just getting started," he said. "It hurt. I wanted to do it because of his reputation . . . It was my turn . . . Wait until next time we meet."