World number one Roger Federer survived a few tricky moments against Arnaud Clement to make the semi-finals of the Estoril Open on Friday.

The world number one was victorious in straight sets 7-6 (9/7) 6-2, although he had to stave off a set point in the opener before securing his passage.

Federer had lost his opening service game to love before fighting back to force the tie-break, which Clement could have closed out only to fire a forehand long.

It was the last chance the world number 83 got as Federer, who is just six weeks away from breaking Pete Sampras’ record of 286 weeks at number one, moved through the gears.

“I got off to a bad start in the first game, falling to 0-30 then he played a great passing shot,” said Federer. “I missed a couple of chances at 3-3.

“I didn’t play beautiful tennis. I had to play safe, which isn’t something I’m used to doing. I have always struggled against him and today you could see that.”

Federer will meet fourth seed Albert Montanes in the last four after the Spaniard took an hour and 30 minutes to beat Uruguay’s Pablo Cuevas 6-4 6-3.

On the other side of the draw fifth seed Guillermo Garcia-Lopez progressed after his fellow Spaniard Albert Martin retired due to a stomach illness when trailing 6-0 2-0.

Garcia-Lopez will play local hopeful Frederico Gil in the last four after he won an all-Portuguese match against wildcard Rui Machado 4-6 7-6 (7/1) 6-3.