The Swiss's pursuit of a modern-era record sixth successive title showed no signs of slowing down when he outgunned, out-thought and ultimately outclassed Croatia's Mario Ancic 6-1 7-5 6-4 to reach his 17th grand slam semi-final in a row.

There he will meet Russian hot-head Safin, who survived a mini eruption in the first set to overcome Spanish 31st seed Feliciano Lopez 3-6 7-5 7-6 6-3.

After days of sweltering sunshine, stormy skies enveloped southwest London, bringing with them rain showers that meant more than three hours play was lost.

Federer's victory charge was briefly halted.

But having blown Ancic off court in the 20-minute opening set for the loss of just one point on his serve, Federer took a two hour rain interruption in his stride and marched towards his 64th consecutive win on grass.

"I'm just very happy I didn't have to burn unnecessary energy," said Federer, the only man who has not dropped a set at this year's championships.

"I was in complete control. I was never really under pressure. I served well. I didn't have to save a break point.

When you go through a match like that... you know you're in a good and comfortable position."

If there was a prize for endurance, Ancic would already have walked away with it. Not only had he taken an exhausting 11 hours 43 minutes to get to the last eight, almost double Federer's time, he also contested 180 games before Wednesday.

In contrast Federer had played 67 fewer games and did not want to linger longer than necessary on Centre Court.

Ancic, who held the distinction of being the last man to beat Federer on grass in the first round here in 2002, finally ran out of puff and was put out of his misery when Federer fired his 15th ace of the match.

QUARTER-FINAL EXPLOSIONS

There was also explosions in the other quarter-final being played simultaneously on Court One

Safin, twice a grand slam winner but now down at 75 in the rankings, became so enraged with his patchy play in the opening set that he fired a ball over the roof and out of the court.

But he managed to put a lid on his emotions in a match which soon turned into a battle of the booming serves.

He out-aced Lopez 18 to 17 and his tally of 45 unreturnable serves was also one more than the serve-and-volley loving Spaniard.

A double fault from Lopez sealed him a place in the Wimbledon semi-finals for the first time but he was not about to get carried away about his chances of ending Federer's five-year reign on Friday.

"To beat Federer you need to be (Rafael) Nadal and run around like a rabbit and hit winners from all over the place. But I think it would be just a little bit too difficult for me to beat him," said Safin, who before this week had not won five successive matches since capturing the second of his majors at the 2005 Australian Open.

Andy Murray was hoping to keep alive Britain's hopes of ending a 72-year wait for a men's champion when he faced Rafael Nadal later on Centre Court on Wednesday.

The remaining quarter-final featured the oldest and lowest-ranked men left in the competition.