ROME (Reuters) - World number one Martina Hingis set up a revenge match with American Serena Williams at the Italian Open Thursday after a 6-1 6-4 third round victory over unseeded American Corina Morariu.

The defending champion won in under an hour and now meets sixth seeded Williams in the quarter-finals -- a repeat of their memorable clash at the Lipton championships in March.

On that occasion, Williams inflicted a rare defeat on Hingis and the Swiss has not forgotten:

``This time it will be different. I'm more confident and I'll take her more seriously,'' said Hingis.

Williams, showing the form which has given her three tournament victories already this season, reached the last eight at Rome for the second successive year with a 6-2 6-3 victory over Irina Spirlea of Romania.

Elder sister Venus Williams, number three seed, kept up hopes of another siblings' showdown in the semifinals -- it would be their fourth head-to-head on the women's tour -- when her power tennis overwhelmed ninth seed Anna Kournikova.

Kournikova, angrily muttering to herself, was beaten 6-2 6-2, and her inability to deal with the pace and depth of the Williams shots left that elusive first title looking further away than ever.

Before thinking about a second successive clash with Serena, however, Venus, winner on clay for the first time in Hamburg last week, must face 11th seed Dominique Van Roost of Belgium, a 6-4 7-6 winner over Nathalie Tauziat.

Number 10 seed Amelie Mauresmo and Swiss Patty Schnyder, whose choices of companions off-the-court have sometimes attracted more interest than their performances on it, let their tennis do the talking in a repeat of their thrilling second round Australian Open match.

Schnyder, mired in controversy for the past three months after leaving home to team up with a German faith healer but reunited with her mother in Rome, took the first set with a single break 7-5.

Mauresmo hit back in the second, taking it 6-2 before, in the 11th game of a close final set, filled with long, grueling rallies, the number five seed's usually steady ground-strokes abandoned her.

She made four unforced errors and lost her serve allowing a grateful Mauresmo to serve out the match and take the final set 6-3 in a repeat of her triumph in Australia.

Like Melbourne, Mauresmo has every chance of going on to make the final after French Open champion Arantxa Sanchez Vicario, seeded to meet Mauresmo in the quarters, was a surprising loser to unseeded Austrian Sylvia Plischke.

Second seed Sanchez Vicario, twice a finalist but never a winner at the Foro Italico, was outplayed in just over an hour on her favorite red clay surface, losing 6-4 6-1 to a player who has found her best form since dumping her coach.

Defeat was a heavy blow for the Spaniard as she prepares for the defense of her French Open crown.

In a repeat of their 1997 Italian Open final, number four seed Mary Pierce saved a match-point and recovered from a set down to defeat four-times Italian champion Conchita Martinez in a third-set tiebreak 4-6 6-0 7-6 (7-2).

Pierce, bidding for her second Italian title in three years, meets either number eight seed Sandrine Testud of France or Israeli Anna Smashnova in the quarters.