Bethesda: Relentless Rory McIlroy showed no mercy to his pursuers in the US Open third round as he extended his lead at Congressional Country Club to an astonishing eight strokes.

Bristling with confidence, the Ulsterman fired a 68 for a US Open record total of 14-under par and he ended the day comfortably clear of South Korea's Yang Yong-Eun, who was alone in second after a 70 on Saturday.

England's Lee Westwood and Jason Day of Australia, who both had 65s, and Robert Garrigus of the United States, with a 68, were a further stroke back.

McIlroy's eight-stroke lead is the largest at the US Open after 54 holes since Tiger Woods led by 10 at that stage at Pebble Beach in 2000. Woods eventually won by a majors-record 15 strokes.

The Irishman also led the Masters after three rounds in April, by four strokes, before ending up in a tie for 15th after a closing 80.

This time, though, the gap at the top of the leaderboard is enormous for a major tournament and it would take an unprecedented collapse for McIlroy to be deprived of his first major title at the tender age of 22.

Playing with Yang, McIlroy started the day with a six-stroke margin, the equal-best-ever halfway lead in US Open history.

He parred the first three holes and then a birdie at the fifth, coupled with a bogey from Yang on the second when he failed to get up and down from a greenside bunker, meant that McIlroy had extended his lead over the Korean to seven.

The Irishman then narrowly missed a long putt for eagle at the ninth, but the ensuing birdie tap-in left him two-under for the day and 13-under for the tournament, eight ahead of the field.

The Ulsterman had blown the field apart in the first two days with rounds of 65 and 66 giving him the lowest first 36 holes in US Open history.

He had stood at 11-under, six clear of second-placed Yang with a group of five players a further three strokes adrift.

McIlroy dropped just his second stroke of the tournament when he failed to get up and down from a bunker at the tricky par-three 10th.

But it was back to business as usual at the next hole, the hardest on the course, which he birdied with a 12-footer and celebrated with a delighted punch of his fist.

His golf was of the tallest order and a six-footer for birdie at the 14th made him the first golfer in US Open history to get to 14-under par.

He stayed there to the end, missing a 10-footer at the last which would have got him to 15 under.

Yang dug in and birdies at 14 and 16 kept him in second and another outing in the company of McIlroy on Sunday.

Westwood, a Ryder Cup partner of McIlroy, began the day seemingly out of it at one-over and he did little of note down the front nine.

But three birdies and an eagle in a four-hole stretch from the 13th suddenly saw him leap into second place as he came in with a tournament equal-best of 65.

"You don't know how Rory is going to do. You don't know how he's going to deal with the big lead," said Westwood optimistically.

The Irishman then narrowly missed a long putt for eagle at the ninth, but the ensuing birdie tap-in left him two-under for the day and 13-under for the tournament, eight ahead of the field.

The Ulsterman had blown the field apart in the first two days with rounds of 65 and 66 giving him the lowest first 36 holes in US Open history.

He had stood at 11-under, six clear of second-placed Yang with a group of five players a further three strokes adrift.

McIlroy dropped just his second stroke of the tournament when he failed to get up and down from a bunker at the tricky par-three 10th.

But it was back to business as usual at the next hole, the hardest on the course, which he birdied with a 12-footer and celebrated with a delighted punch of his fist.

His golf was of the tallest order and a six-footer for birdie at the 14th made him the first golfer in US Open history to get to 14-under par.

He stayed there to the end, missing a 10-footer at the last which would have got him to 15 under.

Yang dug in and birdies at 14 and 16 kept him in second and another outing in the company of McIlroy on Sunday.

Westwood, a Ryder Cup partner of McIlroy, began the day seemingly out of it at one-over and he did little of note down the front nine.

But three birdies and an eagle in a four-hole stretch from the 13th suddenly saw him leap into second place as he came in with a tournament equal-best of 65.

"You don't know how Rory is going to do. You don't know how he's going to deal with the big lead," said Westwood optimistically.

(Agencies)