American golfer Jordan Spieth executed his game plan perfectly in the third round of the British Open, avoiding costly mistakes while also taking advantage of birdie opportunities to give himself a three-stroke lead with a total of 11-under 199.

Spieth on Saturday started the day at six-under total, two shots ahead of countryman and playing partner Matt Kuchar. Both of them were well aware of the need to be aggressive on a mild day at the Royal Birkdale Golf Club with little wind and lots of competitors moving their way up the leaderboard, reports Efe.

The third-ranked Spieth carded three birdies on the front nine and two more on the back nine — the last coming on a long putt on the par-four 18th — in a clean, bogey-free round.

"I'm extremely pleased, couldn't ask for much more. I feel very confident in the way I've been striking my irons," 23-year-old Spieth was quoted as saying by europeantour.com.

"If that continues and I feel that way as we get in our warm-up and then early in the round tomorrow, then I can play more conservatively off the tee and take a lot of those bunkers out of play and that's obviously very important."

Kuchar, 39, kept himself in contention with a 66, although a costly double bogey on the par-four 16th tarnished what could have been one of the lowest rounds of the day. He has a three-day total of eight-under 202.

Several golfers went deep into the red at Royal Birkdale, with South African Brendan Grace shooting an eight-under 62, the lowest-ever single-round score in a men's golf major.

A score of 63 has occurred 31 times at one of the four major championships, but Grace now has a piece of golf history all to himself.

American World No.1 Dustin Johnson also had a remarkable day, firing a 64 that got himself back into the tournament at 3-under 207 total.

Even so, he will likely need both Spieth and Kuchar to have miserable final rounds to have any chance on Sunday.

Four other golfers also are ahead of Johnson: 20-year-old Canadian Austin Connelly and American reigning US Open champion Brooks Koepka at five-under 205 and Grace and Japan's Hideki Matsuyama at four-under 2016.

Stronger winds and occasional showers in Southport, a city on England's northwest coast, could make playing conditions more challenging on Sunday.