McDowell, 28, is chasing his third victory on the European Tour

Graeme McDowell double-bogeyed the last hole to give Jeev Milkha Singh a share of the lead at the Ballantine's Championship in South Korea.

The overnight leader overshot the 18th, taking a drop and finishing with a six-under 66 for 18-under-par 198.

And India's Singh capitalised as he fired an eight-under 64, with five consecutive birdies around the turn.

Paul McGinley carded a second straight 67 to stay four shots behind, while Sweden's Johan Edfors is on 13 under.

Open champion Padraig Harrington chipped in at the 18th to return a four-under 68 and was level with Australia's Kane Webber on 12 under.

606: DEBATE What are your thoughts on Mcdowell's chances of winning this tournament? GJtheaussiestud (U10814819)

World number five KJ Choi failed to mount a charge in front of his home fans, shooting his second successive 69 for a total of 209.

McDowell continued his impressive form as he tore up the front nine in 30 shots.

The 28-year-old Portrush player sunk four birdies and an eagle on the par-five fourth, to put him firmly in the driving seat with only Singh posing a serious threat.

But the Indian rattled off five successive birdies from the seventh and kept the pressure on McDowell as the two men went toe-to-toe in an absorbing duel.

McDowell, who returned a 64 on Friday and is chasing his third victory on the European Tour, claimed further birdies at 12 and 16 before overcooking his approach to the 18th.

"When Jeev made five birdies in a row I knew I had a fight on my hands," McDowell said.

"Obviously it was very disappointing to finish like that."

I still have to do the business tomorrow. Jeev is going to be very hard to shake off Graeme McDowell

The Ulsterman, whose season's best finish was fifth in the Dubai Desert Classic, is chasing a first European Tour victory since the 2004 Italian Open.

He added: "It's a wake-up call but it doesn't change my outlook. I still have to do the business tomorrow. Jeev is going to be very hard to shake off."

Argentina's Ariel Canete signed for a 67 to move to 11 under alongside American Anthony Kim, who shot a three under 69.

Englishman Oliver Wilson was five under for the day to move to five under for the championship.