INDIANAPOLIS, AUG. 19 -- The U.S. baseball team may not have won any Pan American Games medals yet, but it has provided two of the more thrilling events in this Pan American competition. After 10 complete scoreless innings at Bush Stadium tonight, the United States kiddie crop continued to destroy its image as a hit-and-run team by producing two home runs that carried the unbeaten squad to a 4-0 victory over Puerto Rico rivaling its earlier win over Cuba.

New Orleans' own Ted Wood led off the 11th by hitting a home run to right field off relief pitcher Edwin Perez. That was only the third hit of the night for the winners. After consecutive singles, Creighton University catcher Scott Servais tried twice unsuccesfully to bunt.

With two strikes, he launched a three-run homer over the fence in right -- his first of the Games -- to provide an insurmountable cushion.

Cris Carpenter of Georgia pitched the final six innings in relief for the victory, his third of the Games. He came close to being the loser, but got out of a bases-loaded, one-out jam in the eighth by getting Nelson Rodriguez to ground into a home-to-first double play.

As a result of tonight's victory, the U.S. will go into Friday's medal round as the No. 1-seeded team. The reward for the Americans' 7-0 record is they get to play Canada, with a 4-3 record, on Friday night at 8, instead of having to meet Cuba (6-1) in the semifinals. Puerto Rico (5-2), which lost a 1-0 decision to Cuba last week, will get another shot at the Cubans in the first semifinal.

A defensive improvement by the Puerto Ricans over their effort in a 12-10 victory over Canada began right away, compliments of pitcher Jose Ortiz. Largely because he was throwing a wicked curveball, Ortiz faced 14 American batters before any was able to hit one of his pitches out of the infield.

The U.S. didn't come up with a hit until Rick Hirtensteiner slapped a single through the spot vacated at shortstop by the fielder covering second. The U.S. nearly turned a two-out walk to Ted Wood and that subsequent base hit into a rally. But Scott Livinstone's drive to the wall in right-center was hauled in by Puerto Rico's Eddie Ahorrio.

Ortiz caused himself some discomfort by walking too many batters. In thefifth, he issued three straight walks. Fortunately for Ortiz and his teammates, catcher Roberto Santana turned one of the walks into an out when he shot down Don Guillot, the 1987 NCAA stolen base champion, trying to take second.

Tino Martinez, whose 14 hits in 23 at-bats in this tournament gave him a batting average of .609 before the game, flied out to deep left field with two teammates aboard, snuffing out another U.S. scoring chance.

Meanwhile, Gregg Olson, the U.S. starting pitcher from Auburn, was every bit as tough as Ortiz. In fact, Olson -- who never started a game for his college team this past season -- only seemed to get stronger as the game progressed.

He struck out seven Puerto Ricans in five innings, including all three batters he faced in the third and two in the fifth. Ortiz was getting his outs with precision breaking pitches, Olson with 90-mph heat shoulder high.

The U.S. finally got rid of Ortiz in the sixth, without really roughing him up. University of Miami designated hitter Mike Fiore reached base on an infield error, and went to second on Ortiz's second balk of the game. When Wood walked, Puerto Rican Manager Jose Manuel Carradero had seen enough bases on balls -- seven in less than six innings.

But Wilfredo Velez came in with the same kind of average-fastball, tantalizing-curve formula Ortiz had used to befuddle the Americans early. And it was easy to see how the Puerto Rican pitchers had allowed the fewest runs of any staff here through the first five games, including a 1-0 loss to powerful Cuba.

With men on first and second, nobody out, Hirtensteiner's sacrifice bunt down the third base line failed: Fiore was out at third. Livinstone struck out on a crisp curve, and Servais popped to center field to make it the third straight inning the U.S. had left two runners stranded.

"They're frightening," U.S. Coach Ron Fraser said of the Puerto Rican pitchers. "They gave Cuba one run. They're a mature team, with a lot of international experience and they're pumped up. They got our attention with that Cuba game."