Now, Puerto Rico needs one more win to be WBC champion. Then, the country can really cheer.

SAN FRANCISCO (AP) -- A beaming Alex Rios rounded the bases and reached home to a line of jubilant, jumping teammates eager to celebrate.

The surprising Puerto Ricans first eliminated the star-studded United States, then took care of two-time World Baseball Classic champion Japan two days later with a 3-1 victory in Sunday night's semifinal.

Now, Puerto Rico needs one more win to be WBC champion. Then, the country can really cheer.

"We totally showed we can be the new team, the champion nobody expected," said Angel Pagan, center fielder for the World Series champion San Francisco Giants. "It means a lot, but not everything, because we're still missing one more win."

Rios hit a two-run homer, Mike Aviles singled twice and drove in the game's first run, and Puerto Rico reached its first WBC final with a big assist from the bullpen.

Relievers Jose De La Torre and Xavier Cedeno each worked out of jams while pitching key moments after winning pitcher Mario Santiago left in the fifth inning with a forearm injury.

Team Puerto Rico will play in Tuesday night's championship against either the Netherlands or the Dominican Republic. Those teams meet in the tournament's second semifinal Monday night at AT&T Park.

A Puerto Rico team that didn't even gather as a full squad for the first time until March 4 in Fort Myers, Fla., reached the championship round for the first time.

Aviles hit a two-out bloop single to center to put Puerto Rico on the board in the first and singled again to start the seventh before Rios hit a towering drive into the left-field seats.

Unlike the two previous WBC winners from Japan, this team was devoid of major leaguers and couldn't pull off a three-peat. Hirokazu Ibata drove in the team's lone run with an eighth-inning single against Randy Fontanez, but Japan missed a chance with a costly baserunning blunder. It also had the tying run at the plate in the ninth but Fernando Cabrera closed out the win.

The Puerto Ricans -- who eliminated the U.S. on Friday night -- certainly could have been road weary after playing the previous two days in Miami and making a cross-country trip to the Bay Area late Saturday, but Edwin Rodriguez's club looked nothing of the sort in stunning the top-seeded Japanese.

Aviles' hit ended 10 scoreless innings in the WBC for Japan right-hander Kenta Maeda, and Santiago didn't allow a baserunner until Ibata's single up the middle with one out in the fourth.

Team Puerto Rico played sparkling defense. Second baseman Irving Falu made a diving stop to his left to steal a hit from Yoshio Itoi for the first out of the fifth, then made another gem to end the eighth. That came after Japan's uncharacteristic mental mistake in which Ibata broke for third, then retreated to the bag as Seiichi Uchikawa already had neared second. Catcher Yadier Molina ran him down for the tag.

"To me, he's the best catcher in the major leagues right now," Pagan said.

De La Torre walked the first batter he saw before back-to-back strikeouts. That sparked Molina to jump and pump his fist in celebration.

The fans were equally into it on a festive night that even included an Irish jig.

Many in the animated, colorful crowd of 33,683 bounced in their seats while waving flags, blowing horns and pounding Thunderstix -- and, of course, the usual cast of boats and kayaks packed McCovey Cove beyond the right-field fence.

Team Puerto Rico eliminated the star-studded U.S. team with a 4-3 victory Friday in Miami and then sent Japan home empty-handed for the first time in the event's short history.

The Puerto Ricans arrived in San Francisco around 11 p.m. local time Saturday night after losing earlier in the day to the unbeaten Dominicans, 2-0. But Rodriguez made sure being tired wouldn't be an issue, talking to his team throughout the tournament about all the challenges of the WBC.

This team already had rallied from a 3-0 deficit against Italy last Wednesday to stay alive in the tournament.

Rodriguez, the former Marlins manager, appreciated having two players familiar with the ballpark's quirky dimensions: Pagan and former San Francisco right fielder Carlos Beltran, Puerto Rico's DH.

Yet it was left fielder Jesus Feliciano who made a couple of athletic plays.

After lining into a double play to end the second inning, Feliciano ran down Shinnosuke Abe's tough liner to left-center for the first out of the bottom half -- with a noisy band playing just 20 feet behind him.

And Pagan, who this offseason signed a $40 million, four-year contract to stay as San Francisco's center fielder, missed on a sliding attempt to stop Uchikawa's two-out triple in the sixth that rolled to the wall.

Cedeno came in and struck out Abe to strand the tying run.

Maeda hadn't allowed a run over 10 innings while giving up two hits with 15 strikeouts in two wins in this Classic.

Maeda, who tossed a no-hitter last year during a 14-win season for Hiroshima Toyo Carp in Japan's Central League, allowed four hits and one run in five-plus innings.

Maeda retired Pagan on a groundout to start the game, then walked Irving Falu and Carlos Beltran on nine total pitches

The two former WBC-winning Japanese managers were in attendance -- Sadaharu Oh (2006) and Tatsunori Hara ('09) -- and each threw out a ceremonial first pitch, accompanied by Puerto Rican Hall of Famer Orlando Cepeda.

Puerto Rico has beaten Japan in three of their four international meetings, including a 6-0 shutout on Oct. 8, 2011, in the World Cup at Panama when they last played.

Notes: Japan is 17-7 all time in the Classic. ... Tickets were lowered to as little as $8 to boost sagging sales with the U.S. team no longer playing. ... Before the game, Pagan pointed at his jersey with pride, then surveyed the field. "Beautiful, I like the wall," he said. "Different." ... MLB Commissioner Bud Selig is expected for Tuesday's championship. ... Netherlands manager and San Francisco hitting coach Hensley Meulens and former Giants manager Felipe Alou will throw out Monday's ceremonial first pitches. ... A moment of silence was held for Cuban WBC pitcher Yadier Pedroso, who died in a car accident Saturday night at age 26.