Obama, UK's Cameron hit the diplomatic treadmill

Britain's Prime Minister David Cameron listens as U.S. President Barack Obama (L) speaks during an expanded G8 working luncheon with leaders from African countries and others at the G8 Summit at Camp David, Maryland, May 19, 2012.

CAMP ROUND MEADOW, Maryland (Reuters) - U.S. President Barack Obama and British Prime Minister David Cameron resorted to a spot of treadmill diplomacy to tackle the world's problems on Saturday, sweating over the euro zone debt crisis while working out at the gym.

Obama chose an unusual spot for an early-morning bilateral meeting with Cameron on the sidelines of a summit of the Group of Eight major economies at the U.S. presidential retreat at Camp David, Maryland.

Obama called for Cameron at his cabin at 7.15 a.m., before the main meetings started.

"They went to the gym, they walked down there together, had a chat on the way down there and on the way back and had quite a long chat while they were there on the treadmills," a British official said, saying their 35-minute discussion focused on the euro zone debt crisis.

A White House official confirmed the two leaders held talks in the gym, but officials were coy about which leader was the most energetic.

(Reporting by Adrian Croft; Editing by Vicki Allen)