LOS ANGELES (AFP) - Olympic absentee Andy Roddick's decision to give the Beijing Games a wide berth seems not to have been in vain after the American top seed reached the semi-finals of the ATP Los Angeles Classic on Friday.

American Roddick decided weeks ago to skip the Olympics in favour of devoting his hardcourt summer to preparing for the August 25 start of the US Open, which follows immediately.

And following a poor summer campaign which brought a second-round loss in Toronto and a no-show for a stiff neck in Cincinnati Roddick showed his form is back after swiftly dispatching Frenchman Marc Gicquel 6-3, 6-1, thereby matching his best showing on the Californian hardcourts.

Roddick, who played a semi-final in 2002, said his second set was his best for some time.

"That was the first good set in four months. I was moving well and not thinking of every shot.

"I was flowing and that was a good feeling. I'll look back to it as a turning point," said the American, just clinging to Top ten status on ninth in the world after a patchy season mix of two titles but several injury detours.

Roddick, 25, needed a few games to find traction, then picked up his pace to roll to victory in 68 minutes, his 30th of the season and his decision to skip Beijing now looks smart.

"It is ending up being the right thing for my tennis," said the former number 1. "I'll get in two events (LA and Washington) which I needed.

In the semis here he will face German Denis Gremelmayr, the German outsider having accounted for his second seed of the week, following up after beating number four Feliciano Lopez by taking out number five Marat Safin in a 3-6, 6-3, 6-2 turnaround at UCLA.

The Russian raced away to 5-1 but began to stutter as early as the first set, which he twice needed to serve out.

Juan del Potro remained untouchable as the Argentine third seed stretched his summer victory streak with a 7-6 (8/6)), 6-2 win.

The breakthrough teenager, winner of his last two European clay events, moved into a Saturday match-up with sixth seed Mardy Fish.

The soon-to-be married American Fish demonstrated his current personal happiness on court, riding eight aces to a 6-4, 6-4 decision over Florent Serra.

Del Potro has not been defeated since the Wimbledon second round on June 25. He has now won a dozen matches in a row and 13 of his last 14.