Tiger Woods holed a dramatic 12-foot birdie putt on the final green at Torrey Pines to ensure the 108th US Open will go to an 18-hole play-off on Monday.

The world number one will take on Rocco Mediate who came within a whisker of becoming the championship's oldest-ever winner at Torrey Pines on Sunday.

The 45-year-old American carded a final round of 71 to finish on one-under and watched on from the clubhouse as Woods and Lee Westwood came down the 72nd hole needing a birdie to force extra holes.

Both men left themselves with birdie putts, but after Westwood had seen his come up fractionally short, Woods, in typically dramatic fashion, sunk his to ensure the tournament would go to a fifth day.

Westwood finished on his own in third at level-par, while Swede Robert Karlsson (71) continued his superb recent form by finishing in a tie for fourth with American DJ Trahan (72).

Two more Europeans, Carl Pettersson of Sweden and Spaniard Miguel Angel Jimenez, finished on three-over with John Merrick to claim a share of sixth, while Heath Slocum shot a best-of-the-week 65 to finish in a group of five players one shot further adrift in ninth which also included 2006 champion Geoff Ogilvy.

However, the headlines were grabbed by Woods who sense of the big occasion emerged right on cue yet again.

In the final pairing with the Westwood, the world number one was forced to recover from another awful start as he made his third double-bogey of the week at the first.

A further dropped shot followed at the second and he looked in more pain than ever from his troublesome left knee as he struggled through the opening holes of the front nine.

Westwood also dropped a shot at the first, but recovered well and looked much the more consistent of the two men in the early stages.

Indeed, he had the chance to pull two clear of Woods and Mediate at the par-three eighth after a wonderful tee-shot, but was left to rue a lacklustre putt as Woods got up and down from the bunker protecting the front of the green to stay in touch.

Both men then birdied the par-five ninth as Westwood maintained his lead, but the Englishman's challenge faltered badly after the turn as he made three birdies in four holes between ten and 13 to slip off the pace.

Resilient as ever despite some way from his best, Woods birdied 11 to move back into the lead for the first time since the start of the round at two-under and looked to be on his way to a 14th major crown.

But incredibly both he and Westwood fired into the water hazard to the left of the par-five 13th and went on to make bogey to hand the initiative to Mediate who had responded well from back-to-back bogeys at five and six to reclaim the lead with birdies at ten and then 14.

Mediate went on to bogey 15 after a poor drive to surrender the outright lead, but was gifted it back moments later as Woods again paid the price for his continued inaccuracy off the tee to drop a shot at the same hole.

Westwood had hauled himself back level with Woods after a birdie at 14 having driven the green on the 270-yard par-four with his partner having strangely refused the same option.

After pars at 16 and 17 the duo knew they would need a birdie to catch Mediate heading down the last, but both contrived to find sand on opposing sides of the fairway from the tee.

Having laid up, they managed to engineer birdie chances at the par-five, but it was Woods, with the final stroke of the day, who found the cup to deny Mediate and preserve his proud record of never having lost a major championship in which he led heading into the final round.