Defending champion Andre Agassi outlasted fifth seed Gustavo Kuerten to make it to the semi-finals of the Mercedes-Benz Cup in California.

Agassi, who defeated Kuerten in the semi-finals last year, triumphed again but he did not have it his own way in a 7-6 3-6 6-4 win.

Agassi came from 3-1 down to win the first-set tiebreak, hitting a forehand winner off Kuerten's short service return.

Kuerten broke Agassi twice to win the second set, and served two games to love.

In the third set, the pair exchanged service games to love but the crucial break came in the seventh game when Agassi claimed a winner off Kuerten's second serve to lead 4-3.

Kuerten fought back, surviving two match points and seven deuces to hold serve and trail 5-4.

But Agassi served two consecutive aces to set up his third match point, and won with a forehand volley off a short return.

In Saturday's semi-finals, Agassi will meet eighth seed Max Mirnyi of Belarus, who beat Michael Llodra of France 6-4, 7-6 (4). Andy Roddick will meet compatriot Jan Michael Gambill in the other semi-final.

Roddick got the better of Belgium's Xavier Malisse 6-4 6-4 while Gambill saw off Nicolas Kiefer of Germany 7-5 7-6 (7-5).

"My confidence doesn't waver too much," said Roddick. "I believe in the weapons I have.

"I didn't serve as well as I did in my other matches but I was able to pick it up off the ground."