Playing through conditions rejected as unsafe by rivals Sjeng Schalken and Rainer Schuettler on another court, Roddick surrendered just three points on his serve in the first two sets, then spoiled the Belgian's upset bid.

"He definitely raised his level in the third set and I don't know if I maintained mine," Roddick said.

"It was tough. I knew it was a little slick but I didn't think it was that bad. I'm just glad to get through."

Just four matches have been completed in three consecutive rainy days, but Agassi and Roddick advanced in part because they were top US television draws playing at Arthur Ashe Stadium, the top priority court to dry at the US Open.

Instead of facing four matches in as many days to win the title like all their rivals, Roddick and Agassi have Thursday off. But should predicted rain hit Thursday, the men's final would go to Monday for the first time since 1987.

"That's what makes tennis so special -- regardless of the circumstances, two guys usually have to deal with it, have to find a way," Agassi said.

"At the end of the day you are seeing sort of the human spirit try to prevail.

"While it's not comfortable for anybody, sometimes it can lead to some real special moments."

Agassi, the oldest man here at 33, could have to play three matches in as many days to win a ninth Grand Slam title. Every rival would be coming off less rest after he advanced in Tuesday's only completed match.

"It would be really tough," Agassi said. "It would be tough on everybody."

Roddick had given up on playing before the rain eased and he was able to play. Showers halted the match after 44 minutes with Roddick up 6-3, 2-2, and caused slick moments in the match. But playing beat waiting.

"It's just frustrating," Roddick said.

"You want to get out there and play. You have to listen to everybody's theories. Are we going to play Monday? Play four in four days? All die because we're going to play four in four days?"

So how big an edge is not having to?

"Ask me in four days," Roddick said.

"I'm not worried about how many days. I'm not going to get caught up in that. I'm just glad to get through. I don't have to worry about the weather tomorrow."

Ten other scheduled matches did not finish. Dutch 12th seed Schalken led German eighth seed Schuettler 5-1 after 25 minutes. When Roddick resumed, they decided against it, joining 11 other matches on Thursday's schedule.

World number one Kim Clijsters took advantage of 10 unforced errors by French fifth seed Amelie Mauresmo to seize a 3-0 lead after 10 minutes of their quarter-final, the only earlier match to sneak points between raindrops.

Organisers will try to finish the women's quarterfinals and men's fourth round on Thursday, although that means double duty for two women who will see their round of 16 matches that began Monday take four days to end, at least.

Japanese 15th seed Ai Sugiyama led Italy's Francesca Schiavone 7-6, 5-4 and Russian seventh seed Anastasia Myskina led France's Mary Pierce 7-6, 2-0. They will try to complete matters early Thursday.

US sixth seed Jennifer Capriati awaits Sugiyama or Schiavone with a day's rest while French Open champion Justine Henin-Hardenne, the Belgian second seed, will play Pierce or Myskina.

Sugiyama has finally become a scheduling priority with organisers. She was not on Wednesday and missed valuable time on an outer court.

Rain began as she unzipped her racket bag and the match, as most, was called off before late clearing allowed Roddick to finish.

Thursday's other men's resumptions find Thai 11th seed Paradorn Srichaphan leading Australian sixth seed Lleyton Hewitt 4-3, Spanish third seed Juan Carlos Ferrero leading American Todd Martin 6-2 and Guillermo Coria, the fifth seed from Argentina, leading Sweden's Jonas Bjorkman 6-2, 2-0.