SHANGHAI (REUTERS) - American Dustin Johnson pitched in for eagle at the 16th hole to set up a three-stroke victory over England's Ian Poulter at the US$8.5 million (S$10.5 million) WGC-HSBC Champions tournament on Sunday.

He carded a closing 66 to finish at 24-under 264 at Sheshan International with Poulter also shooting 66 for second place on 21-under.

Northern Irishman Graeme McDowell was another shot back in third after also carding 66.

Johnson, 29, collected US$1.53 million for his first victory in a World Golf Championships event and eighth on the United States PGA Tour.

He started the final round with a three-shot lead over Poulter but surrendered it after only two holes, only to come on strong on the back nine.

"I knew if I stuck to my game plan, it would come," Johnson said. "I was swinging well and putting well."