Roger Federer looks in no mood to surrender his US Open title after recording his 38th consecutive win at the tournament.

The five-time defending champion dominated his fourth-round encounter with Tommy Robredo, cruising to a 7-5 6-2 6-2 victory on the Arthur Ashe Stadium on Monday.

The world number one, who will now face Robin Soderling in a repeat of this year's French Open final, held his serve throughout the contest as Robredo was totally outclassed.

The only time the Spaniard looked capable of troubling Federer was in the first set when it took the champion until the 11th game for him to secure the decisive break of serve.

Federer found his rhythm better in the second, with back-to-back breaks of the Robredo serve taking him 5-1 ahead.

He duly served out and refused to take his foot off the pedal in the third.

He was soon 4-0 up and although Robredo salvaged some pride with a couple of service holds, Federer went on to clinch victory with an ace.

Soderling moved into the last eight when Nikolay Davydenko quit their clash due to injury.

Soderling had just taken a two-sets-to-one lead in the pair's fourth-round match when Davydenko offered his hand.

He had been troubled by a left thigh injury towards the end of the third set but it was a tame end.

Soderling was ahead 7-5 3-6 6-2 at the time and appeared to be on course for victory over the two-time semi-finalist.

Soderling's record against Federer does not make for good reading - his loss at Roland Garros in June was his 11th in 11 meetings against the Swiss.

Meanwhile, hopes of a home winner in the men's singles were ended as John Isner was beaten by Fernando Verdasco.

The big-serving American started well enough but, perhaps understandably given his four-hour victory over Andy Roddick on Saturday night, he faded as the match wore on and went down 4-6 6-4 6-4 6-4.

Verdasco, who made the semi-finals at this year's Australian Open, progresses to the last eight at Flushing Meadows for the first time. He will next face Novak Djokovic, who was too good for Radek Stepanek.

Fourth seed Djokovic swept into the quarter-finals with a solid straight-sets victory.

The Serbian former Australian Open champion scored a 6-1 6-3 6-3 win in an hour and 46 minutes over the 15th seed from the Czech Republic but was never really stretched by an inconsistent opponent.

The home fans will instead have to cheer for a winner in the women's draw where the dream run of 17-year-old Melanie Oudin continued on Monday as she moved into the quarter-finals.

Having already accounted for fourth seed Elena Dementieva and former champion Maria Sharapova, the American added 13th-seeded Nadia Petrova to her list of scalps, fighting back for a 1-6 7-6 (7/2) 6-3 victory.

Oudin, ranked only 70 in the world, thrilled the fans on the Arthur Ashe Stadium with another gutsy performance - just as she had done against Dementieva and Sharapova she fought back from a set down.

The youngster, a victim of Laura Robson when the Briton won the Junior Wimbledon title last year, lost the first set badly but raised her game in the second.

Petrova only needed to claim the ensuing tie-break to win the contest but played it awfully.

With a superb 16-4 record in three-set matches this year, Oudin would have been full of confidence heading into the decider.

She squandered a 2-0 lead as Petrova fought back to 2-2 but the Russian's play was too erratic and she soon found herself 5-2 down.

Oudin failed to serve out but didn't let that faze her and simply got stuck into Petrova's serve in the following game.

Oudin moved to triple match point at 0-40 and although Petrova managed to stave off the first two, Oudin clinched victory with a forehand winner.

Oudin's opponent in the last eight will be Dane Caroline Wozniacki, who came from a set down to defeat 2004 winner Svetlana Kuznetsova.

The Danish ninth seed overcame the reigning French Open champion and sixth seed in a third-set tie-break overnight.

Kuznetsova, who committed 63 unforced errors in the match, had been a break up in the final set before surrendering two breaks to Wozniacki, only to break again when the Dane was serving for the match at 5-3.

Wozniacki got match point on the Russian's serve before Kuznetsova held for 5-5 and saved another match point at 6-5 before forcing the tiebreak.

A weak backhand from the sixth seed at the net was the turning point in the breaker, handing a minibreak to Wozniacki and giving the Dane the serve at 5-3. This time there would be no more twists in the ploy and the ninth seed closed out the match to book a place in her first grand slam quarter-final.

Another teenager, Yanina Wickmayer, later joined Oudin in the quarter-finals.

The 19-year-old Belgian won a tight battle against Petra Kvitova 4-6 6-4 7-5, the Czech being unable to back-up her third-round win over top seed Dinara Safina.

Next up for Wickmayer will be unseeded Russian Kateryna Bondarenko, who recorded a famed 'double-bagel' victory in her fourth-round match.

The Ukrainian crushed Gisela Dulko 6-0 6-0 to avenge sister Alona's defeat at the hands of the same player in round two.