Youngster Jordan Spieth moved into a share of the lead at the halfway stage of the AT&T National.
Spieth, who does not turn 20 until July 27, carded a sublime five-under 66 at Congressional to move onto seven under-par overall, alongside overnight leader Roberto Castro.
US Walker Cup star Spieth looked as if he was going to race out in front on his own as he reached the turn in 31, but he parred all the way home to join Castro, who recorded three birdies and a bogey in his two under par round.
"Obviously you start feeling nerves when you know you're at the top of the leaderboard but I was able to to channel them nicely," Spieth said to the PGA Tour's official website.
"They didn't affect my ball-striking and I had a few putts that just barely missed on the back-nine and I'm looking for them to fall tomorrow."
If Spieth goes on to triumph in Maryland, he would - at 19 years, 11 months and three days old on Sunday - be the PGA Tour's fourth youngest winner since 1900.
Play was suspended late on Friday with the pair two shots clear but Andres Romero closed the gap to just one shot after a number of players returned to the course to complete their rounds early on Saturday morning.
The Argentinian actually joined the pair in the lead after back-to-back birdies at the 14th and 15th but a bogey at the 16th left him with a five-under 66.
Belgium's Nicolas Colsaerts moved into a three-way tie for fourth with a birdie at the 16th for a 68, while both DH Lee of South Korea and American Jason Kokrak carded 66s to join Colsaerts on five-under 137.
American trio Cameron Tringale, James Driscoll and Bill Haas are all on four under.