World record holder Haile Gebrselassie has targeted the marathon title at the 2012 London Olympics, some 12 years after his last Olympic gold medal.
The former Olympic and four-times world champion over 10,000 metres told reporters ahead of the Berlin marathon that he was running out of aims.
Gebrselassie, who won Olympic golds in 1996 and 2000 in the 10,000 and four consecutive world titles over the distance, has set consecutive world records in 2007 and 2008 in Berlin on what is considered the fastest marathon course in the world.
Gebrselassie, who opted not to run the marathon at last year's Beijing Olympics because of concerns about pollution, will be 39 by the time the London Games come round.
Kenyan Duncan Kibet will give Gebrselassie a stiff challenge on Sunday after becoming the second-fastest marathon runner, clocking a time that was only 28 seconds off the Ethiopian's world record of 2 hours 3 minutes 59
Gebrselassie said he was not thinking too much about other athletes.
"Since I started marathon, what I found out is that marathon is not like other distances. If you think about only the athletes you miss something. In marathon you run against the distance. Not against the competitors," he said.
"My concentration is in the distance itself and not the athletes. Athletes are one thing but the distance is the most important one.
"If you only think about Duncan Kibet, what about the rest. We all are doing our best race," he added.
Although he refused to speculate about whether a world record was on the cards, Gebrselassie said the fast Berlin course was always about time.
"Berlin always comes with the time. To win is something but to break the record is special," he said, adding he wanted to run under 61.30 minutes at the halfway mark and then would see if a world record was possible.
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