The sport's top female athlete soared an impressive 7.11 metres, the second best leap in the world this year, to convincingly win the women's long jump at the US Olympic trials in Sacramento.

The performance, the best by an American in six years, assured Jones of a spot on the US Olympic team for next month's Athens Games.

The reigning Olympic champion had failed to make the US team in the 100 metres on Saturday, and had been only the seventh-best long jump qualifier on Monday.

But things were so different on Thursday.

Jones on her second jump, bounded 7.11 metres, her best since winning the IAAF grand prix final in 1998, and no one came within 28 centimetres of the performance.

Grace Upshaw finished second at 6.83 metres.

"I think I had just a little bit of motivation," Jones said laughing, as she held a brief question and answer session with the public address announcer.

"It feels really good," Jones said. "I had fun out there. So many people told me, "just have fun out there.

"(But) it was very hard to keep it together today," Jones said as her voice appeared to crack.

Jones later issued a statement saying she 'was very happy with my performance.'

'I am excited about making my second Olympic team and look forward to going to Athens,' she added.

Jones did not speak to the media. She has been under scrutiny by the US Anti-Doping Agency for most of the year although she has never failed a doping test.

She has run poorly in her first year back from the birth of her son with world 100 metres record holder Tim Montgomery. But on Thursday she was in control from the start with jumps of 6.80, 7.11, 6.72, 6.81, 6.84 and 6.72 metres.

She will attempt to also make the US team for the women's 200 metres this weekend.

FAST 400

Young Jeremy Wariner produced the second big performance of the day when he clocked the fastest 400 metres in the world this year, 44.37 seconds.

The 20-year-old Wariner, who attends the same university that world record holder Michael Johnson did, powered down the straight to add the US trials title to his indoor and outdoor collegiate championships.

Otis Harris finished second in 44.67 seconds with Derrick Brew third in 44.69 seconds.

Olympic relay gold medallist Calvin Harrison, who has been charged with his second stimulant positive, placed fifth in 44.85. He could still be named to the 4x400 metres relay team. Only the top three qualify for the individual events.

Dan Lincoln won the men's 3,000 metres steeplechase in 8:15.02.

The trials end on Sunday.