Mickelson birdied the 72nd hole to cap a two-day 72 that left him at 4-under 276, one shot in front of Steve Elkington and Thomas Bjorn.
Besides the champion and the co-runners-up, Davis Love III, Vijay Singh and Retief Goosen -- like Elkington all major champions -- were on the course and under par when the sirens sounded at 10:05 a.m. to resume play on the Lower Course at Baltusrol Golf Club.
Singh was the first of those chasing clubhouse leader Tiger Woods, who completed his 2-under 278 before the threat of severe weather forced the suspension late Sunday afternoon.
The defending champion, Singh missed the 6-foot par putt on No. 16 he had been mulling all night to fall to 1-under. He bogeyed 18 to finish a 74 that left him at even par.
Goosen, a two-time winner of the U.S. Open, came back to play the two closing par 5s but could only par both and was done at 1-under.
Love, the 1997 PGA champion who started the final round as a co-leader with Mickelson at 6-under, couldn't overcome poor drives and parred out to finish tied with Woods at 2-under.
``I was driving it good and I was trying to do things with it to try to keep it in the fairway, and I think that was the difference,'' Love said. ``I just didn't shape the ball real well off the tee like I wanted to.''
Even though the par 5s were long -- 650 and 554 yards -- it was still expected that the birdies would be there for the final pairings.
Among the six in contention, only Mickelson, who got up and down from greenside rough for the win on 18, and Bjorn, who made a 4 on 17, managed to birdie either hole.
``They played very difficult coming in,'' Love said. ``I mean you had to kill it off 17 just to be able to get your short club to the green on your third shot.''
Elkington got a big break on 18 when his tee shot went into the trees on the left only to bounce back into the fairway. His second shot, however, got a bad break when it landed in a divot in the fairway.
``The last place I wanted to hit was the right bunkers so I was trying to guard from that and I overguarded and hit the tree and it came out,'' Elkington said of his tee shot on 18. ``I got a great break and then I hit a nice shot into a divot. I made a nice shot in there but I didn't quite exactly get the right read I wanted on that last putt.''
Bjorn said his birdie on 17 was ``a good drive, a good 3-wood, a great 9-iron and a fantastic putt.''
The 18th was another matter, although he almost made it a birdie-birdie finish.
He hit a good drive in the fairway but pulled his second shot into a greenside bunker. With a tough stance he blasted out to about 20 feet and the birdie putt touched the edge of the cup.
``Everyone in the world thought that was in,'' he said. ``I felt good over it and when it was a foot from the hole I felt even better. It wasn't to be.''
It wasn't to be for five of the six who returned in red numbers Monday.