SHANGHAI (REUTERS) - American Bubba Watson sank a 30-yard bunker shot for eagle at the par-five 18th to earn a spot in a play-off and then drained a lengthy birdie putt on the same hole minutes later to win the WGC-HSBC Champions golf tournament on Sunday.

Watson, the reigning US Masters champion, added another big title to his resume when he holed from about 18 feet at the first extra hole to edge out Tim Clark after the pair finished tied on 11-under-par 277 at Sheshan Golf Club.

The South African missed his birdie chance from about 20 feet, his putt holding a good line but running out of steam just inches from the hole.

Earlier, Clark had birdied the final hole in regulation to card 69, while Watson shot 70 in the same penultimate group.

They finished one shot ahead of Northern Irishman Graeme McDowell, Japan's Hiroshi Iwata and American Rickie Fowler after an exciting final round in which five players were tied for the lead late in the round.

McDowell, who had led the US$8.5 million (S$11 million) tournament for the first three days, and Iwata both had good birdie chances to join the play-off but their putts slid left of the hole.