Top seed Mardy Fish held off a strong fightback by fellow American Ryan Harrison to book his place in the final of the Los Angeles ATP event with a 6-0 4-6 7-6 victory Saturday.

Fish won the third set tiebreaker 7-3 in bright afternoon sunshine, sealing victory with his seventh ace of the match after a see-sawing contest lasting two hours 11 minutes at the LA Tennis Center.

In Sunday's final, the American world number nine will face either compatriot Alex Bogomolov or Latvia's Ernests Gulbis, who were scheduled to play their semi-final later Saturday.

Los Angeles resident Fish, who won his sixth ATP World Tour title at last week's Atlanta Tennis Championship, raised both arms in a mixture of celebration and relief after scraping past the 19-year-old Harrison.

"He kept his level and credit to him," Fish said courtside, having stormed into a commanding 5-0 lead in the tiebreak before clinching the match.

"He came out in the second set and fought hard and didn't give up, didn't let the moment get to him. He could have easily won that match.

"Tiebreakers are kind of a coin flip out here. I was lucky enough to get up there and put some pressure on him at the end."

Fish, who beat Harrison in straight sets in the semi-finals in Atlanta last week, was delighted with his own form in a one-sided opening set at the LA Tennis Center.

"That was probably the best set of tennis I have played all year," the 29-year-old said. "I lost five, six points and it was as clean of a set as I could possibly play."

However, Fish also paid tribute to Harrison, who is widely regarded as one of the most exciting young prospects in American men's tennis.

"This only the second semi-final of his whole career," Fish said. He's way ahead of where I was at 19 and I have a lot of respect for his game."