Roger Federer [ Images ] saved four match points before edging past Belgian Olivier Rochus [ Images ] 6-7, 7-6, 7-6 to reach the semi-finals of the Halle International in Halle, on Friday.

The Swiss world number one, unbeaten on grass since losing to Mario Ancic in the first round of Wimbledon [ Images ] in 2002, was given a real fright in the second set.

Rochus, who at 1.70 metres tall is one of the shortest players on the tour, three times came within a point in the tiebreak of chalking up a memorable win, after earlier holding another match point at 6-5.

Rochus had won the first set tiebreak 7-2.

After staving off the danger, Federer took the tiebreak 11-9 on his third set point to level the match after one hour and 51 minutes.

Rochus refused to wilt under pressure and went 4-2 up in the third until Federer finally produced the goods to keep alive his hopes of a fourth successive title here by winning the tiebreak 7-5 on his sixth match point. The result left the triple Wimbledon champion just two matches away from equalling Bjorn Borg's [ Images ] 41 consecutive wins on grass.

He will next play Germany's [ Images ] Tommy Haas [ Images ] or Robin Soderling [ Images ] of Sweden.