Featuring precarious pin placements and tricky winds, the 99th U.S. Open moved into its treacherous mode today at Pinehurst No. 2, leaving three notable players at the top and Tiger Woods lurking close behind.

David Duval and Phil Mickelson, two of the four co-leaders after the first round, remained in first along with '91 Open champion and '98 runner-up Payne Stewart, all at 3-under-par 137. Stewart was the only one of the three to break par, with a scrambling 69 in the morning; Duval and Mickelson, playing in the same afternoon pairing, each shot even-par 70 and found plenty of satisfaction on a difficult day.

"I thought 70 would be an exceptional score today," Mickelson said. "I would have taken 70 at the start and I'm pleased with 70 at the end."

Woods also was delighted with his round of 71 -- 139, leaving him two shots off the lead in his quest to win his first Open title. Duval and Mickelson, two of the more dominating players of their generation, also are eager to break through for their first major championship at a storied venue.

Pinehurst, which yielded only three under-par rounds today, should offer a more stern defense on the weekend as greens dry out, firm up and reach supersonic speeds under predicted sunny skies and mid-eighties heat. Stewart and Duval will play in the final group Saturday, with Woods and Mickelson paired right ahead of them.

"The conditions are very difficult out there," Woods said after completing a round that began at 7:30 a.m. "The wind's up and it's blowing in the trees. Some of the pin locations, in my mind, are questionable. It's a very difficult golf course."

Woods was in a four-way tie for fourth place, along with two major championship winners, Vijay Singh (70) and Hal Sutton (70), and first-round co-leader Billy Mayfair (72).

John Huston and Jeff Maggert, both starting at 1 over for the day, had the only other sub-par rounds, each posting 69 to tie for eighth place at 140. Bob Estes, Tim Herron, Paul Goydos and Rocco Mediate were four back at 141; Jesper Parnevik and Jim Furyk were among six players at 142, and Davis Love III was in a group of nine at 143. Tom Lehman, in the final group on Sunday at the Open the last four years, just made the cut of 147. Players within 10 shots of the lead make the cut in this USGA event.

Duval, a four-time winner on tour this season, looked for a while as if he were getting ready to leave the field behind, with birdies at the second and fifth holes pushing him to 5 under, the lowest score of the week. But reality quickly set in at the 222-yard 6th hole when a shot out of the rough nearly stopped about 10 feet past the hole, then caught a typical Pinehurst slope and kept rolling off the green.

Duval knocked his third shot to the fringe, then two-putted for a double bogey. He quickly rallied with birdies on his next two holes. But the world's No. 1 player failed to get up and down from bunkers at the ninth and 11th holes and went to 2 under at the 16th after a poor second shot to a deep grassy area led to a 20-foot miss on his par-saving putt. He got that back quickly, too, with a 12-foot birdie putt at 17, and parred the 18th.

"I'm very positive, considering it was a lot more difficult out there and I didn't play quite as well as yesterday and still managed to shoot even par," Duval said. "You have to be very sharp throughout the day. There's not one little hole that's a let-up anywhere. I would think you're going to see players start backing up. The greens will continue to get harder and faster, and even par will be a good position to be in at about 7 o'clock on Sunday night."

Mickelson began with five straight pars, moved to 4 under at the 447-yard 12th hole with a 30-foot birdie putt, then paid the price for a mis-hit drive at the 489-yard 16th. His second shot off a hard, semi-sandy lie caught a greenside bunker, and his 15-foot par-saving putt grazed the right edge but didn't drop, giving him one last bogey before he parred the last two holes.

For his part, Stewart was pleased with his 69.

"The way I got it was not what I envisioned, but it's what I came up with, and that's what you have to do," he said. "One of the reasons I do well at U.S. Opens is that I get a mind-set that par is a good score.

"However I go about making par, whether it's two beautiful golf shots and two putts or two ugly golf shots, a chip and a holed putt, whatever it is I can accept, I take it and go because you're never losing to anyone. You're not losing to the field on any hole if you're making par."

Woods appears to be taking the same approach, though he also is producing some breathtaking shots. One came at the 485-yard eighth, after a drive that landed way right in the pines at the base of a tall tree. Woods had about a 10-foot opening between two trees to the green, then knocked an 8-iron off a pine needle lie to the only place he could, 40 feet from the hole. Then he two-putted for a most improbable par.

At the 610-yard 10th, his second 2-iron shot was short of the green, with a bunker jutting out that left little margin for error. He took out a 3-wood, choked up on the grip and batted it 50 feet within a foot of the cup and made birdie.

"I'm very pleased just to be under par, very pleased," Woods said. "I know how difficult it is out there, and everyone else does, too. But you have to hang in there. You have to keep grinding it out and making the pars. . . . If you go out and make 36 straight pars, you're going to be looking all right. Make 36 pars on tour, and you're 18 back."

Here at Pinehurst No. 2, you hoist a U.S. Open trophy over your head on Sunday night.

CAPTION: David Duval, left, Phil Mickelson, are at 3-under-par 137, along with Payne Stewart. "You have to keep grinding it out," said Tiger Woods, two shots back.

CAPTION: "One of the reasons I do well at U.S. Opens is that I get a mind-set that par is a good score," said Payne Stewart, the '91 Open champion, '98 runner-up.