Andy Roddick has underlined his US Open title claims with a superb 6-3, 6-4, 7-6 demolition of Belgian Xavier Malisse in their rain-hit fourth-round encounter.

The American fourth seed dealt admirably with delays and interruptions as he eased into the quarter-finals on Wednesday with his 16th successive win -- the longest unbeaten streak on the men's tour this year.

Roddick lost just three points on his service in the first two sets, showing why many predict he will be crowned the new men's champion at Flushing Meadows.

The win granted Roddick an unexpected day off on Thursday.

"I try not to get worried about how many days are left," Roddick told reporters.

"I'm just happy to get through and at least I don't have to spend (Thursday) thinking about the weather."

Although Malisse finally found his touch in the third set, even holding two set points at 5-4, Roddick regained his concentration to book a quarter-final meeting with either Dutchman Sjeng Schalken or Germany's Rainer Schuettler.

It is the third successive year Roddick has reached the last eight, and he said: "Now I want to get through this time."

Roddick was the only player to register a result on Wednesday, while Schalken versus Schuettler is one of six men's fourth-round matches still to be completed after rain ruined the schedules for the third day running.

NEW DOWNPOUR

Only Andre Agassi and Roddick have been able to progress into the last eight and, as rain fell for most of Wednesday, it looked as though Roddick would have to wait too.

Eventually he and Malisse walked on court at 9.10 p.m. (2.10 a.m. British time on Thursday) after another rain delay and, in the 44 minutes possible before a new downpour, Roddick went up 6-3, 2-2.

A little more than an hour later, the pair resumed with Roddick as serene as ever.

Yet at 11.12 p.m., with the lightest of drizzle falling, his bid to get the match finished quickly looked in doubt.

Roddick slipped on the slick hard court as he broke for 4-3 in the second set and tournament referee Brian Earley walked out to inspect the court.

Roddick and Malisse both waited courtside for seven minutes before insisting the surface was safe enough to play on.

The brief hiatus did Malisse no favours, and he continued to look like a rabbit caught in the headlights when Roddick let rip with his fearsome, 140 mph (224 kph) deliveries.

"It's the toughest serve I've ever (faced)," said Malisse afterwards.

After conceding the second set, Malisse received treatment for a foot blister at 3-2 up in the third and that was, at last, the cue for him finally to make inroads into Roddick's game.

He held three break points at 4-3 and two break and set points at 5-4, all of which Roddick fought off.

Malisse even held a 5-3 lead in the tiebreak but he could not press home his advantage, and a missed volley on match point helped Roddick close out both the tiebreak 7-5 and the contest in two hours, seven minutes.

Roddick is slowly getting used to late night matches. "My body clock is a little out," he said.

"But I'm feeling more confident...and playing a lot better than I have done in any of the other years here."