LONDON (AFP) - French Open champion Rafael Nadal reached the Queen's semi-finals for the first time after out-lasting Ivo Karlovic in a gruelling three-set clash on Friday.

Nadal, the top seed, had never gone beyond the last eight at Queen's in his two previous visits to the pre-Wimbledon warm-up tournament but he now faces reigning champion Andy Roddick for a place in the final.

The Spaniard was pushed all the way by Karlovic, who showed why his serve is regarded by many as the best in the world, before finally winning 6-7 (5/7), 7-6 (7/5), 7-6 (7/4).

Nadal couldn't break the Croat, a Queen's runner-up three years ago, during two hours and twenty minutes of attritional action, but he managed to win a point on his opponent's serve in each of the final two tie-breaks and that was enough to edge through.

This was grass-court tennis of the most brutal kind and should serve as ideal preparation for Nadal's bid to overthrow Roger Federer at Wimbledon. After surviving this kind of barrage, even Federer's immense talent will seem managable.

At 6ft 10ins Karlovic is the tallest player on the tour and uses his height to devastating affect. He hammered down over 1,300 aces in 2007 and used his heavy artillery to keep Nadal on the back foot here.

Nadal had a break point in the seventh game but Karlovic was able to call on another power serve to subdue the Spaniard.

That was as close as Nadal got to making an impact on the Karlovic serve for the rest of the set.

Nadal constantly wrong-footed Karlovic by putting vicious top-spin on his ground-strokes, but the Croat simply responded by firing down yet more unreturnable serves.

A tie-break was inevitable and it was Karlovic who got the decisive mini-break when Nadal tamely double-faulted.

Nadal saved two set points on his serve but could do nothing about another thunderous Karlovic serve that clinched the set.

The second set was a carbon copy of the first with neither player able to find a way to break serve. Again a tie-break was the only way to seperate them, and this time it was Nadal who snatched the advantage with a perfect passing shot to earn the mini-break he needed to win the set.

By midway through the third set, Karlovic had amassed 32 aces and Nadal, for all his muscular aggression, was no closer to finding an answer. Not that Karlovic was faring any better on Nadal's serve.

The final set tie-break was tailor-made for Nadal to show his ice-cool temperament. He dug in and unleashed a powerful return which caught Karlovic off-balance and secured a mini-break.

Nadal finally saw a chink in Karlovic's armour and held serve to reach the last four.

Roddick advanced without having to complete his match for the second successive round as Andy Murray pulled out with a thumb injury.

Roddick, who reached the last eight when Mardy Fish withdrew after one set, got lucky again as Murray opted not to play because he didn't want to aggravate his thumb problem ahead of Wimbledon.

The British number one suffered the injury against Ernests Gulbis in the previous round and, although an ultrasound scan showed he hadn't broken any bones, he decided be take a cautious approach with the grass-court Grand Slam looming in two weeks.

"I had a scan. I haven't pulled anything. I just sprained it a bit," Murray said. "Obviously it's not terrible, but it's just too sore to try and play a match.

"I've spoken to doctors, physios, the guys on my team, and decided this is the best decision for me."