By Ed Osmond
SANDWICH, England (Reuters) - South African Louis Oosthuizen held his nerve to lead the British Open by one shot after a gripping third round played out in bright sunshine at Royal St George's on Saturday.
Oosthuizen, the 2010 Open champion, had moved serenely to 13 under par with a birdie at the ninth hole before two bogeys, his second and third of the tournament, halted his progress.
Americans Jordan Spieth and Collin Morikawa joined him in a three-way tie for the lead but Oosthuizen then sank a 10-foot birdie putt at the par-three 16th to move back to the top of the leaderboard and carded a 69 to finish at 12 under.
"There's lots of golf left, but it was so great with all the fans there," Oosthuizen told reporters. "It felt like it was a Sunday afternoon really when I made the putt and I was taking the lead.
"I had a few loose swings before that on my iron shots and sort of needed that little boost and made a really good swing on 16 and a few good ones coming in."
Oosthuizen, 38, has finished second in six major championships since his triumph at St Andrews 11 years ago.
"A lead is not like you can just hang tight and just hit a few shots coming in," he said. "You need to still play proper golf and place the ball really well to avoid bogeys."
Morikawa emerged as Oosthuizen's closest challenger, recovering from a poor start to collect four birdies and sign for a 68 that left him on 11 under.
"To be honest, you build a game plan and we see what we need to do all the way in the tournament and I stick to it," he told reporters.
Morikawa won last year's PGA Championship at the age of 23.
"Obviously, being in a final round at a major is different, but I'm going to try and keep it as similar as possible to every other tournament I've played," he added.
Spieth, bidding to lift the Claret Jug for the second time, racked up four early birdies and another one at the 10th took him to 12 under.
The 27-year-old's putter went cold on the back nine, however, a dropped shot at the 11th halting his momentum before he bogeyed the last two holes in a round of 69 to finish at nine under.
Canadian Corey Conners put together a sparkling 66 to get to eight under alongside American Scottie Scheffler, one ahead of Spain's Jon Rahm, Canadian Mackenzie Hughes and South African Dylan Frittelli.
U.S. Open champion Rahm eked out three birdies on the back nine in a battling 68.
"Really good round. Played good golf. Had some really good highlights," the Spanish world number two told reporters.
American world number one Dustin Johnson's challenge faded with a disappointing 73 that left him at four under, while his compatriot Brooks Koepka struggled to a patchy 72 and the four-times major champion ended at three under.
Defending champion Shane Lowry made a gutsy 69 to get to five under but the Irishman conceded he was probably too far behind the leaders to retain the title.
"I'm not sure I can win from here, but I'm proud of myself the way I battled." Lowry told reporters."
(Reporting by Ed Osmond; Editing by Hugh Lawson/Pritha Sarkar/Ken Ferris)