Australia's Brett Coletta shot a 4-under 66 on Tuesday on Olympia Fields' North Course to top the clubhouse leaderboard in the U.S. Amateur when the second-round of stroke-play qualifying was suspended for the day because of darkness.
The top 64 players will advance to match play on the North Course.
The 19-year-old Coletta had five birdies and bogey to finish at 7-under 133.
David Oraee of Greeley, Colorado, coming off his senior season at the University of Colorado, was a stroke back after a 67 on South Course.
Defending champion Gunn Yang of South Korea advanced, following his opening 73 on the North Course with a 69 on the South Course. Yang will be a sophomore at San Diego State.