Beau Hossler, Ryan Armour and Brian Gay were at the top of a heavily contested leaderboard after day two of the Quicken Loans National in Maryland, with Waterford man Seamus Power five shots back after shooting a level-par 70.
Hossler followed up his first-round 65 with a 66, dropping shots on the first and 13th holes, only to recover with back-to-back birdies through holes 14 to 15 and 17 to 18.
Armour fired a blemish-free second-round 65, while American Gay joined his countrymen on nine-under overall after shooting a round of 64 which included five birdies on the front nine.
Italian Francesco Molinari, who is fighting for a place in Europe's Ryder Cup team after an excellent run of form, is one back after a second-round 65.
Tiger Woods also put himself in contention at the halfway stage, moving up the leaderboard into joint 11th on five-under after a round of 65.
Scotland's Martin Laird will not play into the weekend after rounds of 70 and 72 put him on two over, one shot past the cut, while Power sits on four-under and tied for 20th.
