Defending CONCACAF Gold Cup champions the United States have enjoyed a relatively easy run to the semi-finals of the biannual regional championship but now face a stiffer test in the shape of Brazil.

Comfortable 2-0 wins over El Salvador and Martinique set up a 5-0 quarter-final victory over amateurs Cuba, thanks to a sterling four-goal performance by striker Landon Donovan.

In Wednesday's semi the US face Brazil's under-23 team but coach Bruce Arena is still expecting a tough challenge.

"Brazil has brought the best of its young players and Brazil's players are the best in the world," said Arena.

"You can't judge a player by his age, the real issue is the quality."

Brazil have been one of the more exciting teams in a largely lacklustre tournament.

After a defeat to Mexico in their opener, Brazil defeated Honduras and then beat fellow-invitees Colombia 2-0 in the quarter-finals with a pair of goals from Sao Paulo striker Kaka.

This is the second time in six weeks that the two nations will play following a 1-0 win for Brazil's senior team in the opening round of the Confederations Cup last month in France.

In addition to Kaka, the focal point of the side is the Santos duo of midfielder Diego and forward Robinho.

The team mix speed and agility with skilled ball movement, prime traits of some of Brazilian football.

"This (Brazilian) team is good," said U.S. defender Carlos Bocanegra.

"It looks like their work rate is higher than their senior team, especially since they (players) are all still trying to prove themselves.

"They come out with something different every game. They're really dynamic so you really don't know what to expect."

Historically the US have not fared well against Brazil. In 11 meetings dating to 1930, the Americans have lost 10 times.

The lone victory game in the semi-finals of the 1998 Gold Cup where Kasey Keller turned in the finest display of a U.S. goalkeeper in the modern era.

"The US team is very disciplined," said Brazil's under-23 coach Ricardo Gomes. "They have some very experienced players and impressed at the World Cup last year.

"I think they have a pretty good attacking system so we expect a very tough game against them."

While fielding a somewhat inexperienced defence, the US will start a nearly full strength attack with Brian McBride partnering Donovan while Sunderland's Claudio Reyna will marshal the midfield.

Preston North End's Eddie Lewis, who set up four goals against Cuba, could play a key role on the left flank while DaMarcus Beasley, sidelined since July 9 with a sprained ankle, could return on the right side.

Mexico take on Costa Rica in the other semi-final to be played on Thursday in Mexico City's cavernous Azteca Stadium, the site of the final on Sunday. The third-place fixture will be held on Saturday in Miami.

Probable teams:

United States: 18-Kasey Keller, 3-Greg Vanney, 4-Carlos Bocanegra, 6-Cory Gibbs, 2-Frankie Hejduk, 7-Eddie Lewis, 10-Claudio Reyna, 25-Pablo Mastroeni, 17-DaMarcus Beasley, 20-Brian McBride, 21-Landon Donovan.

Brazil: 1-Gomes, 2-Maicon, 3-Luisao, 4-Alex, 5-Adriano, 6-Paulo Almeida, 7-Julio Baptista, 10-Diego, 15-Nilmar, 8-Kaka, 11-Robinho.

Referee: Carlos Batres (Guatemala).