Haile Gebrselassie recently withdrew from a half-marathon

Double Olympic champion Gebreselassie has only just returned to training after tendonitis in his left Achilles tendon and has opted not to take part.

Olympic and world champion Abera has failed to make a recovery after undergoing tendon surgery last autumn.

"I am really sorry to take this decision but I hope to come back again in 2006," said Gebrselassie.

Abera was also disappointed to pull out of the race but he admitted his fitness was a concern.

"After not being able to defend my Olympic title, I was looking forward to London as the next best thing," he said.

"Although I have been training well, I am not at the level it takes to compete in London."

Gebrselassie made his Marathon debut in London in 2002 while Abera triumphed in 2003, edging out Italian Stefano Baldini in a thrilling finish.