Former triple champion Williams won the last four games of her third round clash with Akiko Morigami of Japan to move into the fourth round with a 6-2, 3-6, 7-5 win.

But the American had to battle hard on the dreaded Court Two.

Morigami, who converted just four of 23 break points, had the chance to serve out the match in the eighth game of the final set in a tie which had been suspended from Saturday because of the rain.

Williams's clash with Sharapova will be a repeat of their 2005 semi-final when the American relieved the defending champion of her title.

By the time the 23rd seed had wrapped up her third round encouter, top seed Justine Henin was already back in the locker room having secured her quarterfinal place by brushing aside Switzerland's Patty Schnyder 6-2, 6-2.

The world number one, bidding to win the only Grand Slam title to have eluded her, will face either Serena Williams or Daniela Hantuchova for a place in the semifinals.

"I was surprised the match was so quick," said Henin after her 56-minute Centre Court outing.

"They were very tough conditions with the wind in the court. But I am doing my job perfectly and I concentrate on fighting hard for every point."

Austria's 16-year-old Tamira Paszek shocked Russian 12th seed Elena Dementieva, a quarterfinalist last year, 3-6, 6-2, 6-3, to reach the fourth round on her Wimbledon debut.

The teenager had lost the first set when play was halted on Saturday.

Paszek, coached by Larri Passos who took Gustavo Kuerten to three French Open titles, now faces former US Open winner Svetlana Kuznetsova for a place in the last eight.

Fifth seed Kuznetsova saw off Agnieszka Radwanska of Poland 6-2, 6-3 and Czech 14th seed Nicole Vaidisova defeated Victoria Azarenka of Belarus 6-4, 6-2.

Vaidisova meets defending champion Amelie Mauresmo for a quarterfinal spot while Russian 11th seed Nadia Petrova, who saw off Spain's Virginia Ruano-Pascual 6-3, 7-6 (7/3), goes on to face French Open finalist Ana Ivanovic.

The Serbian sixth seed made sure of her place in the last 16 by beating Aravane Rezai of France 6-3, 6-2.

Serena Williams was 1-1 with Hantuchova in the first set of their fourth round tie when heavy rain, which has plagued the championships, returned to send the players off court.

Later Monday, if the rain relents, Serbian third seed Jelena Jankovic faces France's Marion Bartoli in the fourth round with the winner to face either Michaella Krajicek or Laura Granville for a semifinal place.

Meanwhile, security was stepped up around Wimbledon in the wake of the attempted car bomb attacks in Glasgow and London with even the players unable to drive into the grounds.

A police helicopter hovered above the venue in south-west London while all entrances were protected by a series of vehicle-blocking concrete slabs to foil similar attacks.