(CNN) -- Lee Westwood claimed the halfway lead at the Dubai World Championship as two birdies on the final three holes gave him a two-shot advantage over a six-strong group tied for second place.

Westwood took advantage of lapses by Race to Dubai leader Rory McIlroy and three-time major winner Padraig Harrington to forge his advantage on the Earth Course.

McIllroy, who had charged into the lead at nine-under, slipped up with bogeys at the 14th and 15th while Harrington made a hash of the par-five 18th as he found the water and ran up a double bogey.

It left them tied at seven-under 137 with first round leader Robert Allenby of Australia, Colombia's Camilo Villegas, Louis Oosthuizen of South Africa and England's Ross McGowan.

Swede Johan Edfors also ran up a double bogey on the last which became a testing proposition for the final groupings as the wind got up.

It dropped him back to five under, one of 13 players within four shots of the lead in the battle for the $1.25 million first prize.

Westwood, who won the European money list in 2000 after overhauling great friend Darren Clarke in the final week, looked set to trail Harrington and McIlroy as he remained at seven under par with a run of 13 straight pars.

But as the other contenders faltered, he birdied the 16th then rolled home a confident 20-foot putt on the 18th to follow his first round 66 with a three-under 69.

Harrington, who has yet to win this year, was left to rue his mistake on the 18th which undermined his title bid.

"I'm glad it wasn't Sunday afternoon when I did it," said the Dubliner.

McIlroy made his bogeys by missing two short putts, but was not dwelling on his misfortune as he bids to become the youngest European No.1 since the great Seven Ballesteros in 1976.

"I got off to the perfect start and I have to think I'm still in a good position," said the 20-year-old from Northern Ireland.