CAPE CANAVERAL, Fla. --Britain's first official spaceman,Timothy Peake, says he's ready to run the London Marathon later this month -- from 250 miles up. But he's not expecting to set a PR, or personal record.

The 44-year-old astronaut said he's glad he's had plenty of time to get used to the International Space Station treadmill. One of the biggest challenges, he said, is the harness he wears to keep his feet on the treadmill in weightlessness: It tends to rub his shoulders and waist.

"It's a great challenge that I set myself, and I'm quite glad this is happening later on in the mission," said Peake, a space station resident since December.

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In an interview Thursday with The Associated Press, Peake said he has the harness fitting "pretty well now," and he's got a few training half-marathons and a little longer under his space belt.

The former British Army helicopter test pilot hopes to finish the 26.2-mile race on April 24 in under four hours -- maybe even 3 hours and 30 or 45 minutes "if I'm feeling really good." That's about 2 ½ laps around Earth. He completed the London Marathon in about 3 hours and 15 minutes in 1999.

He'll run at the same time as all the other estimated 38,000 marathoners, including several European Space Agency and UK Space Agency representatives who call themselves Team Astronaut. The point is "to share in a little of Tim's pain," said Jonathan Scott, head of the medical projects and technology team at ESA's space medicine office in Cologne, Germany. Scott will wear a replica Russian launch and entry spacesuit for the entire race -- "to significantly add to the Fun Factor," he explained in a web posting. A UK Space Agency employee, Libby Jackson, also will wear a spacesuit replica.

It will be the second space marathon: U.S. astronaut Sunita Williams took part in the 2007 Boston Marathon, finishing in just under 4½ hours.

Peake's U.S. crewmates, Jeffrey Williams and Timothy Kopra, promise to assist in any way they can.

"We'll check in on him every now and then, and make sure he gets all the food and drink that he needs to make it through it," Williams told the AP.

While he can't exactly carbo-load up there, Peake has managed to fill up on fruit this week: Fresh oranges and apples were aboard the SpaceX Dragon supply ship that arrived Sunday.

Peake and his Team Astronaut colleagues on the ground are running the marathon for the Prince's Trust, a charity set up by Prince Charles 40 years ago to train and educate disadvantaged young people in Britain.