ZAGREB, Yugoslavia (AP) _ Guard Troy Lewis of Purdue hit a 3-pointer with 50 seconds to play Tuesday to lead the United States to an 88-81 victory over Brazil in the World University Games.

Lewis, who had made two free throws in the final seconds Sunday to give the United States an 83-82 victory over Spain, broke an 81-81 tie with the long jumper.

Brazil then turned the ball over on its next possession, and Kansas State forward Mitch Richmond scored on a dunk with 36 seconds to play for an 85-81 lead. Iowa's B.J. Armstrong added another basket just before the final buzzer.

''It was too close for comfort,'' U.S. Coach Mike Krzyzewski of Duke said. ''We just couldn't hit from the outside in the first half.''

The Americans made just 41 percent of their shots from the field in the first half, with most of the points coming from the inside.

''The team played real hard the whole way. Maybe the problem was they were playing too hard,'' Krzyzewski said.

Lewis scored nine of his team-high 13 points in the second half, while Richmond and Duke forward Danny Ferry added 11 points each. Amstrong, Curtis Wilson of Ohio State and Sean Elliot of Arizona scored 10 each.

Brazilian forward Marcelo Vido led all scorers with 25 points.

Brazilian Coach Jose Sobrinho said ''The Americans played good defense and they are very fast. I favor them to win the gold, but not if they keep playing the way they did tonight.''

The United States is scheduled to play Czechoslovakia Wednesday.