The US fumble the baton.

Britain's hopes of adding the world title to their Olympic relay gold got a lift when the much-fancied American team crashed out of the heats in Helsinki.

The US team dropped the baton on the first changeover between Mardy Scales and Leonard Scott leaving former Olympic and world champion Maurice Greene waiting in vain on the final leg.

It means 100m and 200m champion Justin Gatlin, rested for the heats, will be denied the chance of a third gold medal.

The British quartet - featuring three of the victorious Athens team - then finished second in their heat behind Trinidad and Tobago to qualify for Saturday's final.

Jason Gardener, Marlon Devonish and Christian Malcolm combined to give Mark Lewis-Francis a slight lead on the final leg, but the former world junior champion was run down by Darrel Brown.

Lewis-Francis held off Greene over the last 100m in the Olympics but his form remains a concern after he failed to reach the semi-finals here and complained of a hamstring injury.

Malcolm identified Trinidad and Jamaica as Britain's nearest rivals in the absence of the Americans, but Gardener insisted they would be concentrating on their own race in the final.

"I'm very pleased to have achieved our main objective which was to qualify in a good position," said the Bath athlete, who narrowly missed out on a place in the individual 100m final.

"It's unfortunate for the US team, we wish they were there because it's exciting and it's a great rivalry between us.

"But we've got to focus on ourselves, we are looking good and healthy and ready to go.

"We practised well together on making sure of safety first. Now we can look at making minor adjustments and we will focus on our own strengths. We have worked well together since we were juniors so we have a good knowledge to call upon."

Scales, seventh in the 100m in the US Championships, looked to have safely passed the baton to Scott only for it to slip out of his hand.

He said: "We made a pretty good exchange but the baton was sort of slippery and it just slipped out of his hand. We worked a lot on it in practice and haven't missed one hand-off."

A philosophical Greene added: "I just came here for a rainy vacation I guess. It looked like Scott had it and when he pulled it away it just slipped out of his hand.

"The US team never practices enough but everything felt good. It is real simple to pass a stick. You just have to get people in there who know what they're doing. People make it harder than it seems."