The 29-year-old American made five birdies against his first bogey of the week to stand on 14-under-par 199 after 54 holes at Liberty National in Jersey City, New Jersey.
“The biggest thing is continue to hit the ball as well as I’ve been hitting it and allow that to free up my putter,” Reed said.
Mexico’s Abraham Ancer, seeking his first PGA title, was second on 200 with Spain’s Jon Rahm and American Brandt Snedeker on 201 and England’s Justin Rose and Danny Willett and American Harold Varner another stroke adrift. Four-time major winner Rory McIlroy of Northern Ireland and South African Louis Oosthuizen, the 2010 British Open champion, shared eighth on 203.
Reed sank a 17-foot birdie putt at the third hole, put his approach to four feet to birdie the par-five sixth then blasted from a bunker to four feet and birdied the par-five eighth.
After starting the back nine with a birdie, Reed suffered his only bogey so far in the week at 15, finding a fairway bunker and bouncing off a cart path into tree-side brush. But Reed answered with a 10-foot birdie at 17 that lifted him into the lead alone after Ancer had taken a three-putt bogey at 16.
Reed hadn’t managed a top-10 finish since October in China until six weeks ago with a share of fifth in Detroit, which heralded a 10th-place showing at last month’s British Open.