Jones is bidding to make the USA team for the World Championships

Jones, running for the first time since a poor Athens Olympics, faded over the final 100m and clocked 55.03 seconds.

Jamaican Novlene Williams won in California in 51.49, while Australian Olympic 400m hurdles champion Jana Pittman finished in third in 52.33.

Jones won five Olympic medals in 2000 but has since given birth and endured a year of doping accusations.

Jones's boyfriend, world record holder Tim Montgomery, was also unsuccessful on his 2005 debut, anchoring a 4x100m relay team that finished third.

I figured it would take a couple of years for her to comeback Steve Riddick

Montgomery awaits a June hearing before the Court of Arbitration for Sport (CAS) on doping charges by the US Anti-Doping Agency (USADA) in connection with the BALCO drugs scandal.

Jones has also been under scrutiny by the USADA although she has not been charged with a doping violation and has denied using performance-enhancing drugs.

Neither athlete has ever failed a drugs test.

Jones' latest performance will come as a blow to her new coach Steve Riddick, who began working with the runner last September.

Only last week, Riddick said: "Marion is fit. She is ready to go. She is going to run and run tough."

Have Your Say on Five Live Will Jones get back to her best?

However, Riddick said giving birth had affected Jones' performances in 2003.

"I figured it would take a couple of years for her to come back," he said. "When you give life you lose a little bit."

Riddick said Jones was striving to make the US team for August's Helsinki World Championships in both the 100m and 200m and the 4x100 and 4x400 relays.

Her manager Charles Wells added that Jones had no plans to compete in the long jump this year.