Barack Obama, who has returned to the US after a gruelling tour of Afghanistan, the Middle East and Europe is consulting a doctor over his sore hip, a spokesman has said.

The Illinois senator, whose regular trips to the gym have highlighted his youth and fitness compared with the aged John McCain, his Republican rival, had been troubled by the hip complaint before leaving for the overseas trip.

He has blamed it on basketball, his favourite sport. "His hip has been sore from basketball for a few weeks, so he's going to see an orthopaedic doctor," his spokesman Robert Gibbs said.

Mr Obama is a lifelong basketball player, working out on the basketball court every mornng and playing whenever he can with his brother-in-law Craig Robinson, a professional basketball coach. He has managed to sqeeze in a game occasionally on the campaign trail. At one stop during his overseas trip, he shot baskets with U.S. troops in Afghanistan.

His determination to stay fit has earned him detractors, some of whom complain that he has spent more time in the gym than on the campaign trail.

Mr McCain has used his rival's gym-going as a weapon. After Mr Obama cancelled a visit to wounded soldiers at a US medical centre in Germany last Friday Mr MCCain accused the Democrat of a lack of patriotism.

In a TV advertisement deriding Mr Obama for snubbing soldiers because he couldn't turn the visit into a photo opportunity, an announcer says: "He made time to go to the gym, but cancelled a visit with wounded troops."

Mr Obama was caught on a microphone in London at the weekend talking to David Cameron about the importance of taking breaks during the energy-sapping presidential election.

The Tory leader was overheard saying to the senator: "You should be on the beach. You need a break". Mr Obama confesssed that he had not had any time off recently, but would be taking a week in August.

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