Defending champion Ernie Els held off a determined challenge from Argentina's Angel Cabrera to reach the World Match Play Championship semi-finals at Wentworth on Friday.

The world number two was joined in the last four by European Ryder Cup winners Padraig Harrington and Lee Westwood, who edged out Thomas Levet and Retief Goosen respectively in tight quarter-finals.

Miguel Angel Jimenez led Bernhard Langer, who upset world number one Vijay Singh in the first round, by three after 28 holes in a match that will be completed on Saturday.

Els, seeking a record sixth Match Play title, sank an eight-foot birdie putt on the 18th green to seal a one-hole win over Cabrera and set up a clash with Harrington.

"It was a tough match, I didn't play all that well this morning but I got it together a bit this afternoon," Els said.

Els, trailing by one after 18 holes, was unable to break free from Cabrera, who carded two eagles and nine birdies to take the South African all the way.

Els edged ahead with a 30-foot birdie putt at the 29th hole and Cabrera's bogey on the 13th gave the champion a two-hole cushion.

Cabrera refused to lie down, however, making birdie on the par-three 14th and when Els fluffed a pitch from just off the 16th green the match was all square.

Els conjured up another birdie at the long 17th and although Cabrera made birdie at the par-five 18th Els got down in two from well off the green to advance to the last four.

REMARKABLE COMEBACK

Harrington stormed into a six-hole lead against Levet, his Ryder Cup team mate, but the Frenchman staged a remarkable fightback to take the match to the final hole.

Harrington, who broke a club after striking a tree earlier on Friday, sustained a cut thumb after catching his hand on another tree and two bogeys by the Irishman allowed Levet to close in.

Levet cut the gap to one but Harrington closed out the match with a birdie to halve the 18th and win by one hole.

Westwood was always in control of a high quality contest against Goosen, who crushed Jeff Maggert 12&11 on Thursday to record the biggest victory margin in the tournament's 41-year history.

Westwood moved three holes ahead with a birdie on the 18th and extended his lead to five with a 10-foot birdie putt on the 27th.

U.S. Open champion Goosen hit back with a stunning tee shot to three feet at the par-three 10th but Westwood stayed solid, sinking a seven-foot putt to halve the 32nd and leave himself four up with four to play.

COURAGEOUS BIRDIE

The South African delayed the end with a courageous birdie on the 33rd and Westwood then bogeyed the 34th. But the Englishman, World Match Play champion in 2000, matched his opponent's birdie at the 35th hole to seal his semi-final spot with a 2&1 triumph.

Jimenez never trailed Langer, his Ryder Cup captain. The Spaniard was three ahead of the 47-year-old German after 18 holes and he maintained that advantage to close in on a semi-final meeting with Westwood.

Langer had earlier ended Singh's hopes at the first extra hole of their delayed first-round match.

Singh, winner of eight tournaments this season, recovered from three down with four holes remaining to send the contest into sudden death but Langer held his nerve to complete a famous victory.

Els completed a 2&1 victory over Briton Scott Drummond, Cabrera edged out Korean K.J.Choi by one hole, Westwood beat British Open champion Todd Hamilton 4&3 and Jimenez was a 3&2 winner over American Steve Flesch.

Harrington beat American Chris Riley 2&1 and Levet defeated Canadian Mike Weir 2&1.