MUNICH, DEC. 13 -- Pete Sampras battled over three tough sets to beat Goran Ivanisevic, and Michael Chang scored a straight-sets victory over Henri Leconte as the two Americans reached the semifinals of the $6 million Grand Slam Cup tennis tournament today.

Sampras, serving for the match in the second set, suffered his only break and lost the tiebreaker. But he rallied for a 7-6, 6-7, 8-6 victory in 2 hours 24 minutes.

Chang blunted Leconte's aggressive net game with passing shots, 7-6, 6-3. Chang, who upset top-ranked Stefan Edberg in the first round, passed with deadly accuracy against Leconte, who often scored spectacular points with his volley but was also prone to errors.

With no tiebreaker in the decisive set, Sampras, the U.S. Open champion, fought off four break points in the ninth game and then broke the Yugoslav in the 14th to clinch the match. Ivanisevic double-faulted on the second match point.

About 8,000 fans in Munich's Olympic hall gave the two 19-year-olds a standing ovation.

"We were both very nervous out there. It's very exciting to be making so much money," Sampras said. Making the semifinals earns $450,000.

In the tiebreaker, fourth-seeded Sampras hit two brilliant passing shots that gave him the edge. He clinched the set with an ace.

In the second set, there were no break points until a spectacular stop volley gave Sampras one in the 11th game. But Sampras fell behind 40-0 on his serve. He saved one break point with a big serve but netted a volley. He fought off two set points in the tiebreaker but lost on a forehand error.

The American fought off a break point in the third game, then saved four in the ninth. "I thought I had him but he was lucky. But he also served well on big points," No. 5 Ivanisevic said.

Sampras held for a 7-6 lead, then broke the Yugoslav to win the match.