Ballymena's Chris Devlin and Muskerry's Niall Turner need three good rounds to make the final stage of the PGA Tour Qualifying School.
Devlin opened with a level par 71 at Hombre Golf Club near his home in Panama City (Florida) on Wednesday and is tied for 28th, a stroke outside the top 20 and ties who progress to next month's finals.
Former Irish Close finalist Turner had four double bogeys at TPC Craig Ranch in McKinney (Texas) and did well to limit the damage to a five over 76.
The top 21 in Texas will progress to stage two but Turner tied for 78th and six shots outside the current qualifying mark.
Devlin will be disappointed with his opening effort having raced to three-under par through 10 holes. But it could have been worse.
He followed a double bogey six at the second, his 11th, with bogeys at the fourth and eighth to slip back to one-over for the day.
But the Ulsterman, who was a surprise qualifier for the 2008 US Open at Torrey Pines, birdied the par four ninth to keep his qualifying hopes alive.
A total of 34 players with a combined 57 PGA Tour victories - including 2003 US PGA champion Shaun Micheel - - are in action at six venues.
Playing at the same venue as Devlin, Micheel opened with a two-under par 70 to share 11th place with Australia's Peter Lonard tied 37th after a 72.