Great Britain's Martyn Rooney ran his fastest 400 metres since 2008 to win an invitational race at the Mt Sac Relays in Walnut, California, ahead of former Olympic champion Jeremy Wariner.
Rooney, the European bronze medallist, clocked 44.92 seconds, with American Wariner, who won Olympic gold in 2004, second in 44.96secs.
It was the Briton's fastest clocking since he recorded his personal best of 44.60s at the Olympic Games in Beijing and indicated a welcome return to form following a disappointing 2011 in which he failed to make the final at the World Championships in Daegu.
The time was also an 'A' qualifying standard for the London Games.
The 25-year-old, in California for warm-weather training, Tweeted: "44.92, Nice to get an A standard and another win, on to the next one, it's APRIL!"
On Friday, Lawrence Okoye threw a world-leading 66.67m to win the discus.