ARDMORE, Pennsylvania (AFP) - Phil Mickelson repelled a host of challengers in the third round of the US Open on Saturday to hang onto his lead after a dramatic day of jousting among the world's top players.

The American started the day with a one stroke lead, saw six different players overtake him, and then rebounded at the death to move back ahead by the smallest of margins on one-under 209.

It was a compelling day which gave the big crowds at Merion Golf Club an ever-changing tableau of golfing fortunes and it set the stage for a last-round dogfight on Sunday with 14 players grouped within six strokes of the leader.

And once again, magical Merion came out on top, with only Mickelson remaining under par as the gnarled old course once again bared its fangs.

Three players - Charl Schwartzel (69), Steve Stricker (70) and Hunter Mahan (69) - were one back on level par 210, with Luke Donald (71), Justin Rose (71) and Billy Horschel (72) a further stroke back.

The 42-year-old crowd favorite Mickelson, seeking a US Open win after a record five runner-up finishes, and in-form countryman Horschel started the day in the lead at one under but were soon reeled in by the chasing pack.

Australia's John Senden, with one win in 10 years on the US tour, briefly took over before being joined by world top tenners Rose and Donald.

Then Schwartzel, the 2011 Masters champion, made his move as the fancied English pair, both of whom are aiming to become the first from their country to win the US Open since Tony Jacklin 43 years ago, briefly faltered.

Former world number one Donald rejoined the South African atop the leaderboard at one under with his second birdie of the day at the eighth and, for the first time in the round, there was clear water between the leaders and the rest of the field.

Schwartzel and Donald stayed ahead for several holes before American Mahan emerged from the pack with four birdies in seven holes down the back nine to become the seventh player to edge his nose in front.

But after Schwartzel, Mahan and Donald all bogeyed the tough par-three 17th, Mickelson got the biggest cheer of the day when he birdied the same hole.

That put him back ahead for the first time since he bogeyed the third hole and put him in sight of the prize he says he cherises the most.

There was no place on the leaderboard for the two biggest names in the game - Tiger Woods and Rory McIlroy.

Four strokes back of the lead at the start of the round and playing together for the third day in a row, the American and the Ulsterman got off to the best of possible starts by sinking 12-footers for birdies at the first.

But McIlroy drove out of bounds at the second for a bogey and they both dropped shots at the par-three third after under-cooking their tee-shots.

They both then bogeyed the fifth as the much-anticipated challenges from the two top-ranking players in the world badly fizzled out.

By the time they trudged off the course, Woods (76) and McIlroy (75) were respectively nine and eight shots adrift of the leaders and, to all intents and purposes, out of contention.

"It certainly is frustrating," said Woods.

"At Augusta (Masters) I was pretty close and I had the lead at one point and I hit that flag and ended up in the water.

"This week I was cleaning up the rounds and I'm one shot off the lead starting the last day without any three putts. And I'm playing well enough to do it and unfortunately just haven't gotten it done." Two of the best rounds of the day came from American Rickie Fowler, who had a 67 to stay in contention at three over, and Australian Jason Day, who carded a 68 to move up to two over.

Sergio Garcia's woes continued when he had a nightmare 10 at the par-four 15th, a hole where he took an eight in the first round, en route to a 75 and an 11-over par total.

There was little joy also for Masters Champion Adam Scott of Australia, who was also well out of the reckoning at 10-over par after a 73.