Vijay Singh survived a battle of nerves to win the WGC-Bridgestone Invitational on Sunday.

Singh shot a two-under-par, final-round 68 at the Firestone Country Club to win by a shot from overnight co-leader Lee Westwood and a hard-finishing Stuart Appleby while Phil Mickelson, who had also started the day with a share of the lead, slipped back to a tie for fourth place with Retief Goosen after finishing with back-to-back bogeys.

It was a hard-fought victory, the Fijian's first since taking the Arnold Palmer Invitational in March 2007, and 32nd on the PGA Tour, making him the most successful international player of all time after passing Englishman Harry Cooper.

Nerves were frayed for all three co-leaders, England's Westwood playing alongside Singh in the final pairing of the day at Firestone Country Club, with Mickelson of the United States playing one group in front alongside Australia's Appleby.

Westwood had also begun the day with a chance of breaking a 10-year winless streak in the United States, his only PGA Tour title among his 27 career victories worldwide having come at the 1998 Freeport-McDermott Classic in New Orleans.

The leading trio began their final rounds at eight under par, one stroke in front of Appleby with first-round leader Retief Goosen another two shots back on five under.

Westwood began with birdie at the opening hole and all three leaders birdied the second, for Singh the first of three in a row that sent him into the outright lead at 11-under.

Westwood began to unravel a little with a bogey at the par-four fourth, and a double bogey followed at the par-three seventh as he slipped to seven under, four shots adrift of Singh and three behind Mickelson.

Yet Westwood was not finished and at the next hole, he birdied as Singh bogeyed and the pattern was repeated at the 11th as the Englishman moved to nine under and the Fijian dropped to 10 under.

Mickelson birdied 11, Singh rejoining him at 11 under with a birdie at the 12th, which Westwood parred.

The 13th saw Westwood birdie and Singh bogey and when Mickelson dropped his first shot of the day at the 15th, all three were tied again at 10 under.

Nerves were clearly affecting all the leaders as Goosen and Appleby began to cut the gap on the front three, both men taking birdies at 16 to move to eight under, with Miguel Angel Jimenez, Clarke and Australian Peter Lonard in the clubhouse at seven under.

The momentum swung away from Westwood yet again at the 14th when he used his putter from the fringe of the green for his third shot, uphill and 46 feet from the hole. He came up 17 feet short, missing the par putt by a fraction to send him behind a shot from the lead.

Mickelson found a fairway bunker at the 17th, laid up on the fairway and sent his approach to back fringe from which he could only manage bogey, while playing partner Appleby kept applying the pressure with birdie.

Westwood scrambled par at the 16th having reached the green from the rough and Singh missed a seven-foot birdie putt.

It left Singh in front at 10 under with two to play, one shot ahead of Westwood, Mickelson and Appleby.

Mickelson found the trees to the right off the 18th tee and then a bunker front and left of the green, from which he reached the right fringe 25 feet from the hole. His par putt missed to send him to eight under while Appleby just missed his 18ft birdie putt, tapping in to finish at nine under and leaving Mickelson out of the running.

Singh began the last with a one-shot lead and he had a birdie putt to win from 26 feet but left it short by around four feet. That gave Westwood a chance to force a play-off from 16ft but he pulled his putt wide and Singh needed to hole out from just three-and-a-half feet for victory.

For once the nerves held.

Paul Casey posted the low round of the day, a five-under-par 65 that earned him a tie for eighth place at six under for the tournament thanks to a bogey-free final round.

"The lack of bogeys today, that was good," Casey said. "The goal was to get top 10.

"I'm just very, very happy with that. The whole week got better as it went on. I started with a triple on the first day on the first hole, which is about as bad as you can start, and it's gotten better since then."

A double bogey at the par-five 16th took the momentum away from Ian Poulter as he closed with a round of 71 to finish the tournament two under par but Open champion Padraig Harrington completed his preparations for next week's final major of the year with a closing 67 to finish at 279, one under par for the tournament.

All 80 of the golfers who teed off in the first round began the fourth round in the no-cut event, with England's Nick Dougherty continuing his improvement at Firestone following opening rounds of 72 and 76. He posted a one-under-par 69 on Saturday and opened with an eagle two at the par-four first, holing out from the fairway with a 129-yard wedge shot.

Dougherty finished the day with a second consecutive 69 to give him encouragement heading to Oakland Hills next week, despite finishing six over par for the week.

Collated final round scores & totals

(USA unless stated, par 70):

270 Vijay Singh (Fij) 67 66 69 68

271 Lee Westwood (Eng) 70 65 67 69, Stuart Appleby (Aus) 70 66 67 68

272 Phil Mickelson 68 66 68 70, Retief Goosen (Rsa) 66 71 68 67

273 Darren Clarke (NIrl) 70 71 65 67, Peter Lonard (Aus) 69 66 72 66

274 Paul Casey (Eng) 70 71 68 65, D.J. Trahan 69 67 70 68

275 Hunter Mahan 71 66 70 68, Miguel Angel Jimenez (Spa) 70 66 70 69

276 Sean O'Hair 68 67 73 68, Chris DiMarco 68 70 68 70

277 Daniel Chopra (Swe) 67 74 66 70, Chad Campbell 68 71 68 70

278 Zach Johnson 67 68 72 71, KJ Choi (Kor) 73 67 70 68, Ian Poulter (Eng) 70 68 69 71, Henrik Stenson (Swe) 73 70 68 67

279 Robert Karlsson (Swe) 71 67 71 70, Justin Leonard 68 70 70 71, Robert Allenby (Aus) 71 70 70 68, Steve Lowery 75 67 70 67, Tim Clark (Rsa) 67 71 71 70, Scott Verplank 71 70 70 68, Padraig Harrington (Irl) 69 75 68 67

280 Rory Sabbatini (Rsa) 69 67 70 74, Vaughn Taylor 72 67 69 72, Oliver Wilson (Eng) 71 69 72 68, Nick O'Hern (Aus) 70 68 71 71, Charles Howell III 68 70 70 72, Justin Rose (Eng) 71 70 68 71, Jim Furyk 68 69 71 72, Ernie Els (Rsa) 69 74 69 68, Paul McGinley (Irl) 70 67 72 71

281 J.B. Holmes 69 68 72 72, Anthony Kim 71 72 70 68, Trevor Immelman (Rsa) 75 64 68 74, Sergio Garcia (Spa) 69 72 68 72, Richard Finch (Eng) 69 75 70 67, Brendan Jones (Aus) 69 73 69 70, Angel Cabrera (Arg) 72 73 68 68

282 Steve Stricker 68 69 75 70, Aaron Baddeley (Aus) 79 69 66 68, Richard Green (Aus) 72 73 70 67, Stewart Cink 68 68 74 72, Brandt Snedeker 68 76 69 69

283 Hidemasa Hoshino (Jpn) 75 73 65 70, Steve Flesch 70 70 73 70, David Toms 72 72 70 69, Stephen Ames (Can) 69 71 71 72

284 Niclas Fasth (Swe) 71 71 72 70, Woody Austin 71 70 72 71, Rocco Mediate 68 73 71 72, Chez Reavie 68 74 70 72

285 Rodney Pampling (Aus) 69 71 75 70, Fredrik Jacobson (Swe) 71 71 70 73, Ross Fisher (Eng) 69 73 70 73, Graeme McDowell (NIrl) 70 71 73 71, Adam Scott (Aus) 69 76 72 68

286 Steve Webster (Eng) 68 72 72 74, Nick Dougherty (Eng) 72 76 69 69

287 Lucas Glover 70 75 72 70, Andres Romero (Arg) 73 71 73 70, Scott Strange (Aus) 68 74 73 72

288 Kenny Perry 74 69 73 72, Boo Weekley 72 73 71 72

289 Prayad Marksaeng (Tha) 70 73 73 73, Geoff Ogilvy (Aus) 71 67 79 72, Martin Kaymer (Ger) 72 79 68 70

290 Brett Rumford (Aus) 75 70 76 69, Johnson Wagner 70 74 75 71

292 J J Henry 69 73 73 77, David Howell (Eng) 70 75 70 77, Soren Hansen (Den) 75 73 70 74

294 Pablo Larrazabal (Spa) 72 75 71 76

295 Colin Montgomerie (Sco) 72 71 76 76

296 James Kingston (Rsa) 73 72 71 80

297 Craig Parry (Aus) 70 75 75 77

301 Mark Brown 80 75 76 70