FLUSHING, New York (Ticker) Teenagers Martina Hingis and Venus Williams overcame long-time tour veterans in fourth-round action today, moving one step closer to an expected semifinal showdown at the U.S. Open Tennis Championships.

Hingis, the top seed and 1997 champion, continued her mastery of 10th seed and 1994 champion Arantxa Sanchez-Vicario of Spain with a hard-fought 6-4, 7-5 win. The 18-year-old from Switzerland extended her winning streak against Sanchez-Vicario to 12 straight matches.

The 19-year-old Williams, who lost the Open final to Hingis in her debut two years ago and is seeded third this year, came back to defeat fellow American Mary Joe Fernandez, 2-6, 6-1, 6-0.

In other fourth-round matches involving seeded women, No. 12 Barbara Schett of Austria earned a quarterfinal meeting with Williams by crushing Elena Likhovtseva of Russia, 6-0, 6-1, and unseeded Anke Huber of Germany ousted her second consecutive seed when she took out Australian Open runner-up and 15th seed Amelie Mauresmo of France, 6-4, 6-4. Huber, who knocked off No. 8 Jana Novotna of the Czech Republic in the third round, will meet Hingis in the quarterfinals.

The start of play was delayed more than two hours due to rain this morning and rain twice interrupted play during the afternoon, pushing many matches back into the evening session.

Hingis and Sanchez-Vicario were scheduled to play the third match of the day on Arthur Ashe Stadium, but they found themselves taking the court under the lights at 7:30 p.m.

Sanchez-Vicario, who won only 11 games in her last three meetings with Hingis, fared better this time, making Hingis work for every point. But her ability to run down shots was tested and eventually overcome by Hingis' steady groundstrokes and pinpoint placement.

Hingis raced out to a quick 4-1 advantage in the opening set, but Sanchez-Vicario broke back to even the set at 4-4. Hingis held serve and closed out the set with a service break.

Sanchez-Vicario went up a break in the second set, but this time it was Hingis who answered right back. The players stayed on serve until Sanchez-Vicario served to stay in the match at 5-6. She hit an overhead wide to set up match point and Hingis cashed in immediately with a forehand winner up the line on the next point.

Williams was in trouble early, but bad luck again befell Fernandez, who sustained a strained right quadriceps when she slipped on the wet surface two games into the second set. Williams went on to take the second set easily, 6-1, and cruised to victory in the third. Fernandez managed to win only one of the final 11 games.

Fernandez, who is unseeded, appeared on her way to a possible upset as she broke Williams on her first three service games and took advantage of numerous errors to win the opening set.

Williams attributed her slow start to a lack of singles activity following a walkover victory over Henrieta Nagyova of Slovakia.

"I haven't played a singles match since Wednesday," she explained. "In the beginning, I couldn't find my rhythm and she was making great shots. I finally started playing better.

"I wasn't worried. I've been down before in matches. Even without the rain delay, I would have found a way. I just got on track in the second set and started playing more consistently and she wasn't making the great shots she was making in the first set. I got caught up in her game. I play a power game and she plays a finesse game. I had to play my game."

Williams fought off two break points on her first service game of the second set and broke for a 2-0 lead and then disaster struck Fernandez.

As she moved to her left for a backhand, Fernandez lost her footing on the wet surface and sustained the muscle strain. Play was halted for more than an hour due to the rain and Fernandez returned with her thigh heavily taped, but she provided little resistance the rest of the way.

"It was terrible," said Williams of the fall by Fernandez. "It wasn't bad at the beginning of the point but after six or seven strokes, the rain was really coming down. I felt bad when I saw her go down. It's unfortunate because she just came back from a wrist injury."

Fernandez said the injury affected her more mentally than physically.

"It was tight. It was sore and Venus was playing a lot better," Fernandez said. "Against her, you have to be 110 percent. I was a little tentative and she started playing great. She started serving really well and she steamrolled after that.

"It was an injury that really wasn't hurting me but I was tentative because of it. It's in the back of your mind all the time. My movement wasn't what it was earlier. My balls were landing shorter and she was able to dictate play. Once she got the lead, it was tough to come back."

Among the men, seventh seed Todd Martin of the United States needed just 36 minutes to advance to the fourth round earlier today as Magnus Larsson of Sweden retired with a knee injury after losing the first set, 6-3.

Martin reached the round of 16 at the U.S. Open for the first time since 1995. Earlier this year, he made the quarterfinals at the Australian Open and Wimbledon.

Martin's next opponent will be ninth seed Greg Rusedski of Britain, the losing finalist here in 1997. Rusedski, who lost in straight sets to Martin in an opening round Davis Cup tie earlier this year, ousted unseeded American Chris Woodruff, 7-5, 3-6, 6-3, 6-4, tonight.

Among other seeded men in third-round action tonight, fifth seed Gustavo Kuerten of Brazil opposes Goran Ivanisevic of Croatia, and 14th seed Tommy Haas of Germany tangles with Hicham Arazi of Morocco.

Jiri Novak and Slava Dosedel, a pair of unseeded players from the Czech Republic, assured their country of a representative in the quarterfinals with victories tonight.

Novak advanced to a fourth-round meeting with Dosedel when Fabrice Santoro of France retired due to injury in the third set of their third-round match. Novak led at the time, 6-1, 6-0, 5-1. Dosedel moved on with a 7-6 (7-5), 7-6 (8-6), 6-3 victory over Swedish qualifier Fredrik Jonsson.

Two other third-round matches featuring unseeded men have yet to be completed. Former Open finalist Cedric Pioline of France faces Peter Wessels of the Netherlands and Magnus Norman of Sweden plays Richard Fromberg of Australia.

Kuerten, a former French Open champion, will be trying to advance to the fourth round of his fourth consecutive Grand Slam event. He reached the quarterfinals of the French Open and Wimbledon before losing.

Ivanisevic has beaten two qualifiers to reach the third round and has lost five of his last six matches to seeded players at Grand Slam events. Overall, Ivanisevic is 10-16 against seeded players in Grand Slam play.