It is because of fears the air pollution in Beijing could bring an early end to his career, according to his manager.

 

Gebrselassie is the marathon world record holder, having moved up to the distance in 2004 following his fifth place in the 10,000 metres at the Athens Olympics.

 

However the Ethiopian distance great, a four-time world champion and double Olympic champion in the 10,000m, is known to suffer allergies to pollen.

 

Breathing problems were cited when Gebrselassie pulled out of last year's London Marathon, in which he finished third in 2002 and ninth in 2006.

 

And the humid climate of Beijing during August, along with concerns over pollution, are giving Gebrselassie some food for thought, according to his manager Jos Hermens.

 

Hermens said: "He is definitely very worried aboute climate and pollution.

 

"He has some problems with his lungs and he is 34."

 

On Friday Gebreselassie set a time of 2 hours 04min 53sec, the second fastest time ever for the 26 mile event, on his way to winning the Dubai marathon.

 

Hermens added: "He would like to run until the London Olympics. If conditions are too bad in Beijing, his career could be over."

 

Hermens said in the event the Ethiopian great decides against the marathon, he could aim to compete in the 10,000m - although with competition stiff among the Ethiopians, he would still have to qualify.

 

He said: "He has not made any plans yet, but he is very concerned.

 

"We still have time and there are several options.

 

"Maybe he will run the marathon, or the 10,000 metres or both.

 

"He still has to qualify for the 10,000m."

 

The issue of pollution is one of the International Olympic Commitee's biggest concerns ahead of this summer's Games.

 

Last August, a year ahead of the Olympics, IOC President Jacques Rogge said the endurance events could be postponed in the event of pollution hitting peak levels in Beijing.

 

In December, air pollution in the Chinese capital was so bad that people were advised to stay indoors.

 

Gebrselassie meanwhile does not intend to compete in marathons as he finetunes his form for Beijing in the coming months.

 

Instead he will compete in the Lisbon half-marathon on March 16, and a 10,000m at Hengelo in the Netherlands on May 24.

 

Gebrselassie set a world record time of 2:04:26 for the marathon in Berlin last September.