Greene at centre of relay row

Greene (middle) and Drummond (right) in the dispute

Maurice Greene has walked out on the US team's first relay practice, fuellling speculation of a row within the quartet.

Greene, the world champion and world record-holder for 100m, took no part in the baton-changing session.

He left the Olympic Park track more than an hour before the practice was complete along with Jon Drummond and their lawyer Emmanuel Hudson.

The relay row is believed to involve Hudson's management company, HSI, exerting pressure to ensure the inclusion of Curtis Johnson and Brian Williams in the 4x100m line-up.

Last year, the Americans fielded a quartet of Drummond, Tim Montgomery, Brian Lewis and Greene to win the world title in 37.59sec, the fifth fastest time ever.

It gets ugly every four years whenever there's someone who isn't selected

  Assistant US team coach Johnny Moon

But last month in Berlin, in unfavourable conditions, the scratch HSI quartet clocked 37.65, comfortably beating the "official" United States squad.

After Greene's departure for the athletes' village, his coach John Smith was seen having a long discussion on the infield of the training track with Johnny Moon, the US team's assistant coach responsible for the men's sprint relay.

Moon was conciliatory in his approach, saying: "Major practice does not start until Monday, after the individual 100m is out of the way."

But he firmly denied that he was being put under any pressure over the team selection.

"I will pick the team - I will have my choice, and someone else will have any choice. If you asked my mother who would be in the team, she would have a different view.

"It gets ugly every four years whenever there's someone who isn't selected.

"But we are men, we can shake hands when we disagree."

'Drive for Five'

Meanwhile, Marion Jones could be given the crucial third leg in the 4x400m relay - her fifth and final event in the "Drive for Five" gold medals in Sydney.

Jones worked on baton changes with her sprint relay team mates Monday, and won a glowing report from coach La Verne Sweat.

"She looked real good today," Sweat said.

"We have some issues with some people," Sweat said. "We'll probably work with them on baton changes after the individual 400m.

"Marion will maybe run the third leg in the final, but I'm still not sure yet."