By Mark Lamport-Stokes

OAKMONT, Pennsylvania (Reuters) - Irishman Shane Lowry held a two-shot lead after 14 holes when third-round play was suspended for the day in fading light at the weather-hit U.S. Open after a long Saturday at Oakmont Country Club.

Lowry, showing steely nerves on a challenging layout running fast and firm, mixed five birdies with two bogeys to get to five-under for the tournament before the horn sounded to halt the action at the 8.49 p.m. (0029 GMT).

"My game is good, I feel very comfortable out there," said Lowry, who moved two strokes clear after hitting a superb wedge to within three feet at the par-five 12th and knocking in the birdie putt.

"Quite happy that we didn't have another four holes to play. It's been a long day. This is right where you want to be (in the lead).

"I'm really looking forward to tomorrow," said the 29-year-old from Clara in County Offaly, who won the biggest title of his career at the 2015 WGC-Bridgestone Invitational.

PGA Tour rookie Andrew Landry, the surprise first-round leader, was at three-under after 13 holes, with American Dustin Johnson, after 13, England's Lee Westwood, after 15, and Spaniard Sergio Garcia, after 14, a further stroke back.

Johnson, who missed a three-foot putt at the final hole to hand last year's U.S. Open to Jordan Spieth, had been one ahead after the delayed second round ended earlier on Saturday but fell short of replicating his form from the first 36 holes.

"It's this golf course," nine-times PGA Tour winner Johnson said after recording two birdies, two bogeys and a double at the par-four third. "It's tough to make putts on it.

"I'm still feeling good about where I'm at. A lot of golf to go. Golf swing feels good, so I'm happy with where I'm at."

SURGING GRACE

South African Branden Grace was the leader in the clubhouse at one-under 209 after firing 66 to surge into contention for the year's second major championship.

"The guys up there (at the top) are playing some great golf," Grace said after sinking a 15-foot birdie putt at the par-four last.

"I stayed patient the whole day ... but when I had the chances, I took them. It was a bonus finishing the way I did."

Just two strokes behind Grace was the ominous figure of Australian world number one Jason Day, who made an explosive start with four birdies in his first five holes on the way to a matching 66 that included an eagle at the par-five fourth, his 13th hole.

"Shoot anything under par here, you're definitely moving up a lot," said Day, the game's hottest player over the past 12 months with seven tournament wins, including last year's PGA Championship at Whistling Straits.

American world number two Spieth also made an early move up the leaderboard with three consecutive birdies in his first four holes but faded to shoot 70 and fall nine strokes behind Lowry.

The 25 players who did not complete the third round will resume at 7 a.m. ET (1100 GMT) on Sunday before the regulation 72 holes are completed by the end of the day.

(Editing by Andrew Both)