Asked if he realized Roger Federer had won 35 straight points -- yes, 35 -- on his serve, Feliciano Lopez blinked his green eyes.

"On his serve?" he repeated.

Maybe he was clarifying the stat, maybe he was in disbelief. No matter Monday night. Federer was off to play Andy Roddick in the quarterfinals at the US Open.

The streak came out of nowhere.

The match was tied going into the third set, and Federer was down 040. Then, over a span of nine games, he won every point he served.

Think about it: All it would have taken was one strong return by Lopez. One slightly off shot by Federer. One double-fault.

Nothing. Not until was too late, right as Federer closed out the final game.

Told the remarkable number, Federer was curious -- and impressed.

"What are you talking about?" he said. "That's awesome."

"Oh, come on. What have I done?" he said, playfully. "I should have broken him to win 6-3 so I wouldn't have to serve it out."

Federer wound up winning 3-6, 6-4, 6-1, 6-4 in the fourth round, rallying after the Spanish lefthander caused him some early trouble.

"I was under a lot of pressure tonight," Federer said.

Hard to tell, especially when he

got rolling. Trying for his fourth straight US Open title, the No. 1ranked Federer faces No. 5 Andy Roddick.

Federer has done pretty well against the 2003 champion and the runner-up last year. To the tune of 13-1, including nine straight wins.

"It's a great record, but it doesn't help me," Federer said. "We'll see how it goes. Andy's always tough at the US Open."

Roger Federer of Switzerland returns a shot to Feliciano Lopez of Spain during their match at the US Open tennis tournament in New York, Monday, Sept. 3, 2007.

Roddick is the only American left, marking the first U.S. Open since 1998 without at least two in the quarterfinals. James Blake had a chance to join in, but missed on three match points and lost to No. 10 Tommy Haas 4-6, 6-4, 36, 6-0, 7-6 (4).

Earlier in the tournament, Blake ended his 0-for-9 slump in five-set tries. His rooting section, the rowdy J-Block, did its best to cheer him on, but the sixth-seeded Blake couldn't come up with thatlast, winning shot.

"It's going to sting for a little while," he said. "Just another unfortunate learning experience."

Haas will play No. 4 Nikolay Davydenko in the quarters. He eliminated Lee Hyung-taik 6-1, 6-3, 6-4.

Earlier, Roddick was leading 7-6 (6), 2-0 when his fourth-round opponent, No. 9 Tomas Berdych, stopped playing because he had trouble breathing and felt sluggish.

"I haven't been tested much this tournament, so far," said Roddick, who immediately went to the practice court to hit for nearly an hour.

Almost from the get-go, Roddick knew Berdych was ailing.

"I heard him say something to the umpire early on in the first," Roddick said. "Then, of course, I'm trying to

eavesdrop on his whole conversation he's having with the trainer."

Said Berdych: "It wasn't any, like, straight one problem or one pain or something. Just like, generally didn't feel well."

On the women's side, former champ Svetlana Kuznetsova beat Victoria Azarenka 6-2, 6-3 and

moved on to play Agnes Szavay. The 1 8-year-old player from Hungary defeated Julia Vakulenko 6-4, 7-6 (1).

Also, No. 18 Shahar Peer beat No. 30 Agnieszka Radwanska 6-4, 6-1, and No. 6 Anna Chakvetadze stopped Tamira Paszek 6-1, 7-5.

Roger Federer's shoes are seen as he serves to Feliciano Lopez of Spain during their match at the US Open tennis tournament in New York, Monday, Sept. 3, 2007.

On Tuesday night, top-seeded Justine Henin plays No. 8 Serena Williams in the most attractive match of the day.

Also in action are No. 2 Rafael Nadal and No. 3 Novak Djokovic.

Concerned that the two women's quarterfinals set for Wednesday --

Kuznetsova vs. Szavay and Chakvetadze vs. Peer -- weren't dazzling enough, U.S. Open officials changed the schedule.

The match between six-time major champion Venus Williams and No. 3 Jelena Jankovic was shifted from Tuesday to Wednesday night, with both players' approval.

Blake, one of the most popular players in the tournament, only wished he was still going on.

"I was a little indecisive at the end there," he said. "Did come down to one or two points there. It's frustrating I didn't win them this time."

The crowd was crazed throughout the final set, then fell into virtual silence at the end.

Haas hit a 113 mph ace that Blake challenged, and the players looked at each other as the crowd became quiet with a mix of anticipation and apprehension.

The replay on the scoreboard confirmed the ball was indeed good, and it was over.

"I'm not going to celebrate like crazy right in front of him," Haas said.