World indoor champion Francena McCorory ran the year's fastest women's 400 metres as she held off Olympic gold medallist Sanya Richards-Ross at the U.S. championships in California on Saturday.
McCorory powered home in a life-time best 49.48 seconds to edge Richards-Ross by 0.18 seconds as the two Americans became the first in the world to dip under 50 seconds this year.
"I ran my lights out today," a delighted McCorory told reporters after the victory on a warm afternoon in Sacramento.
"It was also great running against a great field and you know the times will be good."
Richards-Ross, who is recovering from toe surgery, also appeared pleased.
"I went hard and got in striking distance," she said.
Beijing Olympic gold medallist Dawn Harper Nelson used a big lean to beat former collegiate champion Queen Harrison in the women's 100 metres hurdles final.
Harper Nelson got out of the blocks in a hurry and prevailed in a quick 12.55 seconds despite a headwind of 1.6 metres per second.
Harrison was a mere hundredth of a second back and bobsledder-hurdler Lolo Jones claimed third in 12.65.
"I think I had a better start this time," said Harper Nelson. "I made a little mistake in the middle and I was like 'Oh lord, don't let it go.'"
World champion Brianna Rollins was fifth in 12.81.
London gold medallist Brittney Reese fought back to win the women's long jump in 6.92 metres as she overtook 100 metres winner Tianna Bartoletta, a former world champion in the jump.
Erik Kynard had a dominant day in the men's high jump, the 2012 Olympic silver medallist clearing 2.35 metres before trying unsuccessfully three times at a national record 2.41m.
Other winners included London Olympics silver medallist Leo Manzano in the men's 1,500m (3:38.63), Sharon Day-Monroe in the heptathlon (6,470 points), Gil Roberts in a depleted 400 metres (44.53 seconds) and Emma Coburn in the women's steeplechase (9:19.72).
The championships conclude on Sunday.
(Reporting by Gene Cherry in Raleigh, North Carolina; Editing by Greg Stutchbury)