Top seed Federer crushes Berdych

Federer had struggled in his previous outing

Top seed Roger Federer was in sublime form as he crushed Tomas Berdych 6-3 6-2 6-3 to book his quarter-final berth at the French Open.

The world number one struggled in his last match against Nicolas Massu but was back to his best on Sunday.

Berdych, who handed Federer a rare defeat at the 2004 Olympics, managed a brief rally when he took a 2-0 lead in the third set.

But Federer recovered and will now face Croatia's Mario Ancic.

"I feel like I'm really into the tournament so from here on, my form is only going to get better," said the world number one.

"I'm obviously looking forward. As usual now it really gets interesting."

Ancic caused a minor upset when he beat Hamburg Masters champion Tommy Robredo 6-4 4-6 2-6 6-4 7-5.

I have worked hard and it's paid off Mario Ancic

In a dramatic final set, Ancic vomited and had treatment for cramp in the middle of a game before booking a rematch against the man he beat at Wimbledon in 2003.

"I believe I'm a better player now than I was and I've improved since the start of the season," said Ancic.

"I have worked hard and it's paid off. I've always had a fighting spirit, I always give 100%."

Third seed David Nalbandian secured his place in the last eight with a 6-4 6-4 6-4 win over fellow Argentine Martin Vassallo Arguello.

Nalbandian will now face sixth seed Nikolay Davydenko, who needed four sets to get past former winner Gaston Gaudio.

Davydenko eventually won 6-3 6-4 3-6 6-3.

French teenager Gael Monfils ended American interest in the men's draw with a 6-2 6-7 (2-7) 7-6 (7-1) 5-7 6-4 win over James Blake.

The match was delicately poised at one set all when play was suspended by bad light on Saturday.

But backed by a fiercely partisan crowd on Court One, Monfils broke at 5-4 in an enthralling fifth set before confidently serving out the victory.

After the match, Blake argued at length with the umpire about the crowd noise.

"A couple of times the fans said things during a point or during my service motion," said the American.

"I didn't feel like he did anything about it. He didn't feel like I had a valid point. We disagreed a bit."

Monfils goes on to face fellow teenager Novak Djokovic for a place in the quarter-finals.

In another match postponed on Saturday, Ivan Ljubicic completed his comeback from two sets down against Argentine Juan Monaco to book a place in the fourth round.

The fourth seed was 4-2 up in the fifth set when play ended on Saturday and he wasted little time wrapping up the two games he needed to complete a 4-6 5-7 6-3 6-4 6-2 win.

Ljubicic, the only remaining seed in his quarter of the draw, now meets Spain's Ruben Ramirez Hidalgo.