LOS ANGELES — America's national pastime took a major hit tonight. On home turf, no less.

Daisuke Matsuzaka remained undefeated in the World Baseball Classic and defending champion Japan beat the United States 9-4 in the semifinals at Dodger Stadium.

Japan advanced to Monday night's title game against South Korea, a 10-2 winner over Venezuela in Saturday's semifinal. Japan won the inaugural tournament in 2006, defeating Cuba in the final.

Akinori Iwamura's RBI triple was the key hit in a five-run fourth inning against starter Roy Oswalt, and the U.S. was handed its first loss to Japan in major international play since the 2005 World Cup. The Americans had won four in a row, including an 8-4 victory in the bronze medal game at the Beijing Olympics.

The WBC has hardly been a showcase for the United States, despite having a roster loaded with major league stars.

Three years ago, the Americans were eliminated 2-1 by Mexico in the second round of the tournament after beating Japan 4-3 during pool play in Anaheim.

This time, the Americans came into their first final four appearance hobbled by injuries.

During the second round in Miami, they lost second baseman Dustin Pedroia (left side), first baseman Kevin Youkilis (sprained left ankle, left Achilles' tendinitis) and reliever Matt Lindstrom (strained right rotator cuff). Chipper Jones (right side) was replaced for the semifinal by Evan Longoria.

The Americans were the visiting team on a cold, blustery night in Los Angeles, having earned the designation by finishing second in Group 2. Japan won Group 1, with South Korea coming in second.

Matsuzaka allowed two runs and five hits in 4 2-3 innings. The Boston Red Sox ace struck out four and walked three before being pulled when he reached 98 pitches, two shy of the 100-limit for the tournament's final two rounds.

Matsuzaka, who pitched six shutout innings against Cuba last Sunday, is 3-0 in this year's WBC, having allowed 14 hits and four runs in 14 2-3 innings. He went 3-0 and was selected tournament MVP three years ago.

Oswalt got tagged, giving up six runs and six hits in 3 2-3 innings. He walked four and struck out one. The Houston Astros right-hander was 1-1 in three WBC starts, allowing nine runs, seven earned, in 11 1-3 innings.

The United States took a 2-1 lead after three innings on Brian Roberts' leadoff homer in the first and David Wright's RBI double in the third.

Japan broke loose in the fourth, with the help of an error by Roberts at second base that made two of the runs unearned. Roberts was added to the U.S. roster before the second round, replacing Pedroia.

Atsunori Inaba and Michihiro Ogasawara opened the inning with singles and the error by Roberts allowed Japan to tie the game 2-all. Kenji Johjima followed with his second sacrifice fly before Iwamura tripled into the right-field corner.

Munenori Kawasaki then singled home Iwamura. One out later, Hiroyuki Nakajima hit an RBI double on a 3-0 pitch, chasing Oswalt and giving Japan a 6-2 lead.

That put the Americans in a big hole against a team that came into the semifinals having outscored its opponents 36-9 in seven games.

But the U.S. got back in the game in the eighth on a two-run double down the left-field line by Mark DeRosa off Takahiro Mahara, cutting the deficit to 6-4. Mahara avoided further damage by striking out pinch-hitter Evan Longoria and getting Roberts to ground back to the mound.

Japan tacked on three insurance runs in the bottom half off Joel Hanrahan and Scot Shields. The first scored on shortstop Derek Jeter's two-out throwing error. Ichiro Suzuki added an RBI single, and Nakajima had a run-scoring double that right fielder Adam Dunn appeared to lose in the lights.

Japan's fans chanted, waved red-and-white flags and pounded orange Thunder Stix during their country's big fourth inning.

Chants of "U-S-A! U-S-A!," which had quieted down for a while, fired back up in the eighth only to be silenced again. The Americans, who celebrated so vigorously after rallying to beat Puerto Rico for a semifinal berth, had no reason to party this time.

The announced crowd of 43,630 — second-largest in WBC history and the most on U.S. soil — was bundled in jackets and blankets as temperatures hovered in the 50s and wind whipped the palm trees in the outfield. There were large pockets of empty seats throughout the stadium.

The Americans blew a scoring chance in the fifth. Jeter hit a one-out single and Jimmy Rollins walked. Matsuzaka then threw a called third strike past cleanup hitter David Wright before reliever Toshiya Sugiuchi struck out Dunn to end the threat.

Rollins went 4-for-4 with a walk and a two-out triple in the seventh. Masahiro Tanaka struck out Wright to end the inning.