American Steve Marino shot a flawless five-under-par 65 to surge two shots clear midway through the first round of the AT&T National at Congressional Country Club on Thursday.

The 28-year-old, playing his second full season on the PGA Tour, birdied three of the first four holes to set the tone for the day before signing off with his fifth birdie of the round at the par-four last.

"There was very little wind, the greens were perfect and soft, so you could really throw some iron shots in there," said Marino, who grew up in nearby Fairfax, Virginia.

This week's tournament is hosted by Tiger Woods but the world number one was forced to skip the event to recuperate from an operation on his left knee following his triumph at last month's U.S. Open.

Woods's team mate at Stanford University, 35-year-old Notah Begay III, was among six players tied for second at 67.

Marino conceded "there's a long way to go" in his bid for a maiden PGA Tour title.

"The guy that's leading the first round I would say the majority of the time, they don't go on to win the tournament," he said.

"The tournament really doesn't begin pretty much until the back nine on Sunday if you want to win."

Joining Begay two strokes off the pace were Germany's Alex Cejka, Americans Billy Mayfair, Tommy Armour III and Anthony Kim, and Australian Stuart Appleby.

"This course is very difficult from tee to green," said Begay, a four-time winner on the Tour. "You have to hit some fairways and put the ball in the right spots on the greens and if you do, you're going to hit some good putts.

"I could easily have shot five or six under today. I missed several putts inside six feet."

Holder K.J. Choi of South Korea carded a two-under 68 to lie three strokes off the early pace.