Tyson Gay ran the second fastest 200 metres of all-time, 19.62 seconds, on a wet track at the US championships on Sunday.
Only fellow American Michael Johnson's world record of 19.32 seconds at the 1996 Atlanta Olympics is faster.
"I was running scared," the 24-year-old Gay said after completing a 100-200 metres double at the meeting, the US trials for August's World Championships.
"I wasn't thinking about any time. I was trying to get away from (world silver medallist) Wallace Spearmon as fast as I could."
Spearmon, Gay's training partner, finished second in 19.89 with Rodney Martin third in 20.18. Olympic and world 400m champion Jeremy Wariner took fourth in 20.35. Olympic champion Shawn Crawford was seventh and last in 20.51.
"The time was excellent. The race was excellent, too," said Gay, who ran into a slight headwind.
The win came after Xavier Carter, the previous second fastest at 19.63 seconds, crashed out in the semi-finals with a dislocated knee cap problem.
Gay had taken the US 100m championship in a season-leading 9.84 seconds on Friday. He will run both in the World Championships and said another US sweep might be possible in the 200m.
World champion Allyson Felix won the women's 200m final in 22.34
US 100m champion Torri Edwards claimed third in 22.55 and La Shauntea Moore was fourth in 22.58.
Two-time Olympic silver medallist Terrence Trammell won the men's 110m hurdles in 13.08 seconds. US record holder Dominque Arnold clocked 13.17 for second and David Oliver took the third US spot in 13.18.
Allen Johnson, the 1996 Olympic gold medallist and four-time world champion, finished seventh in 13.60 seconds. He had made every US world championship team from 1995.
Alan Webb surged ahead of two-time Olympic medallist Bernard Lagat in the final 30m to win a stirring 1,500m in 3:34.82. Kenyan-born Lagat slipped to third in 3:35.55, finishing behind Leonel Manzano (3:35.29).
Khadevis Robinson dominated the men's 800m in 1:44.37, outrunning upcoming American Nick Symmonds (1:45.17).
American record holder Jenn Stuczynski won the women's pole vault at 4.45m and Tiffany Williams ran the year's fastest women's 400m hurdles in 53.28 seconds.