By Steve Keating

RIO DE JANEIRO (Reuters) - The United States and Spain finally lived up to expectations, posting blowout wins on Wednesday to reach the semi-finals of the Olympic men's basketball tournament as France and Argentina lost much more than a game.

While the United States and Spain have struggled to reach their full potential at times on the Rio hardwood, Australia and Serbia have delivered much more than expected in also reaching the last four.

Even though the United States were the only team to finish group play without a loss, questions about their ability to claim a third straight gold swirled after three unimpressive narrow wins to close out the preliminary round.

Those questions were answered in the form of a 105-78 rout against Argentina as the U.S. extended their Olympic winning streak to 23 games.

"We got our swagger back, offensively and defensively," Team USA guard Paul George, a three-time NBA All-Star, declared to reporters.

Second-ranked Spain made a poor start to the tournament with losses to Brazil and Croatia before shifting into top gear with four straight wins, including a 92-67 victory over old foes France on Wednesday to ease into the last four.


Basketball fans can now savor the prospect of a mouth-watering semi-final between the U.S. and Spain that could double as an NBA All-Star game as both teams are stacked with NBA champions, All-Stars and most valuable players.

"This is another challenging team, so we have got to come in right," George said about Spain. "They're good. Another team full of pros.

"They have a little bit of everything. They have shooters, big men, ball handlers, scorers.

"All of those guys are pros and they have played together for a while so they have some experience."

Ranked 11th, Australia may be an underdog but they have been one of the top teams in Rio and punched above their weight on Wednesday with a 90-64 upset win over third-ranked Lithuania to close in on what would be a first ever Olympic basketball medal.

"It's another step on our journey," said Matthew Dellavedova, one of four members of the Australian squad who have NBA championship rings. "We've set the goal of winning a gold medal and today was just another step."

The next step for the close-knit Boomers is a semi-final meeting with Serbia, who came out on top after a hard-fought Balkan derby as they held off Croatia 86-83.

As France and Argentina made their quarter-final exits, they not only said goodbye to Rio but also bade farewell to standout players who put their respective countries on the basketball map.

Tony Parker, 34, confirmed after the loss that he had played his final game for France.

Just a few hours later, his 39-year-old San Antonio Spurs team mate Manu Ginobili followed suit by calling an end to his international career with Argentina.

(Additional reporting Mary Milliken; Editing by Mark Lamport-Stokes)