PEBBLE BEACH, United States (AFP) - United States PGA Tour rookie Andrew Loupe fired an eight-under par 63 at Monterey Peninsula on Thursday to grab the lead at the rain-hit Pebble Beach National Pro-Am.

Loupe was headed to the first tee early on Thursday just 39 minutes into the first round when play was suspended because of standing water on some of the greens on the three courses in use for the first three rounds of the tournament.

After a delay of almost three hours, play got underway and Loupe was able to get into the clubhouse with a career-best round that gave him an unexpected two-stroke lead.

Forty players failed to finish and were to return early on Friday to complete their rounds.

"I just keep telling myself, you're supposed to be here, you're going to play good, just keep playing," said Loupe, who had eight birdies and no bogeys.

"And this is just one round, guys, you know, but I feel good."

Loupe, 25, had only broken 70 once in 11 previous rounds on the US PGA Tour. In five prior starts this season he has yet to make a cut.

He only secured his card with an equal sixth-place finish in the final event last season of the Web.com Tour's Finals series.

Jimmy Walker, who leads the tour's Fed Ex Cup play-off standings, was among five players tied for second on six-under par.

He posted his 66 on the par-72 Pebble Beach Golf Links, where Sunday's final round will be held after everyone in the field plays one round at the par-71 Monterey Peninsula, par-72 Pebble and par-72 Spyglass Hill.

Australians Stuart Appleby and Scott Gardiner and Americans Jim Renner and Richard H. Lee all carded six-under 65s at Monterey.

Jordan Spieth fired a bogey-free 67 at Spyglass and was tied at five-under with Robert Streb, Brian Harman and European Ryder Cup captain Paul McGinley of Ireland.

Streb and McGinley posted 67s at Pebble Beach while Harman's 66 came at Monterey Peninsula.

Four-time tournament winner Phil Mickelson was among those who failed to complete their rounds. He was five-under through 15 holes.