Louis Oosthuizen opened up a one-shot lead in a gripping final round at the U.S. Open.

Oosthuizen was in a three-way share of the lead heading into Sunday at Torrey Pines but was initially circumspect, going one over through eight.

That put the 2010 Open winner a shot behind defending champion Bryson DeChambeau, who came agonisingly close to a sensational hole-in-one at the par-three eighth.

That birdie result was enough for the outright lead on five under at the turn, although the American's first bogey of the weekend on 11 came as Oosthuizen's putter heated up, picking up shots on nine and 10. Oosthuizen dropped one at 11 though.

DeChambeau erred again, meaning Jon Rahm – who flew out of the blocks with back-to-back birdies – was the nearest challenger to Oosthuizen alongside another overnight leader Mackenzie Hughes on four under.

Rory McIlroy drained a 35-footer on the fourth, leaving him well-placed early on minus four.

However, the Northern Irishman passed up three further birdie opportunities by the midway point of his round and his hopes were fading when he bogeyed the 11th.

That left McIlroy level on three under with Brooks Koepka, although the American four-time major winner was through 16 holes and appeared to have missed his moment to make a decisive move.

The 2020 US PGA champion Collin Morikawa was one of the pack on four under until he went through the green on 13 and left with a double bogey.

Louis Henley was alongside Oosthuizen and Hughes in the clubhouse on Saturday but also dropped back to minus two, albeit in less spectacular fashion than Morikawa.