Defending champion Andre Agassi wasted little time in dispatching Max Mirnyi of Belarus at the Nasdaq-100 Open on Monday, wrapping up a 6-2, 6-2 third round victory in just 52 minutes.

The fourth-seeded American moves on to a showdown against Agustin Calleri for a place in the quarter-finals after the Argentine advanced with a 6-4, 7-6 victory over Australian wildcard Todd Reid.

"It feels good," Agassi said. "Days like this are few and far between so I definitely feel great about the performance but I'm experienced enough to know how quickly things can turn around.

"I was pretty fortunate with the way it went today."

The home crowd were treated to another American victory when Andy Roddick overcame a determined challenge from Jonas Bjorkman to beat the Swede 6-4, 3-6, 6-3.

The match was also a dress rehearsal for a Davis Cup quarter-final tie in just over a week when Roddick is likely to face Bjorkman again as the U.S. take on Sweden at Delray Beach.

"Obviously you can't help but think forward but winning tonight really doesn't do anything to help our chances in the Davis Cup," Roddick said.

The second seeded Roddick plays Guillermo Canas next after the doughty Argentine overcame Belgium's Xavier Malisse 6-4, 2-6, 6-3.

WILLIAMS'S ADVANCE

In the women's event, second seed Venus Williams joined sister Serena in the last eight with 6-1, 6-3 victory over Italian 15th seed Francesca Schiavone.

"I was playing a very good player and a real fighter," Venus said. "So it was really good for me to get out there and make a point of getting through this match."

Top seed Serena was also in a hurry, easing past Russian teenager Maria Sharapova 6-4, 6-3 to earn a place in the quarter-finals.

Playing only her third match since returning from an eight-month lay-off, Serena defeated the 16-year-old in an hour and 15 minutes.

"Today and yesterday I was a bit sloppy but confidence-wise I feel like I'm getting better with every match," she said.

Her opponent agreed.

"It doesn't matter how long she was out for. You have to expect the best from her," Sharapova said. "She's not number one in the world right now but she's still a champion."

Having been delayed for more than two hours by light rain, Serena looked anxious to see off Sharapova quickly, hitting 26 winners to the Russian's two.

Serena, who beat Marta Marrero and Elena Likhovtseva in previous rounds, now plays Jill Craybas after the unseeded American overcame ninth seed Paola Suarez 4-6, 6-4, 7-6.

The Nasdaq-100 Open is Serena's first tournament since she won Wimbledon last July. She underwent knee surgery in August 2003 and missed the U.S. and Australian Opens.

"You don't understand how happy I am," she added. "Just to be out there competing is a really big step for me."