Long-distance legend Haile Gebrselassie wants to carry on running until the 2012 London Olympic Games.
Gebrselassie is running in his third London Marathon
The double Olympic 10,000m champion will contest his third London Marathon on Sunday.
"I have no plans to retire - I am serious about still running in London 2012," the 34-year-old Ethiopian told BBC Sport.
"Running is in my blood and I mean to keep on running. Every athlete dreams of the Olympics."
Gebrselassie, who won brilliant back-to-back 10,000m Olympic titles in 1996 and 2000, is already focused on reaching next year's Olympic Games in Beijing.
He said: "It's not difficult for me to qualify for Beijing as there are very few marathon runners in Ethiopia.
"If I ran a good time before the Games and I am not injured it will be good to run in Beijing."
My career is very long and I want to close it in style
Stefano Baldini on his plans to retire after the 2008 Olympics
Gebrselassie, who won both the Berlin and Fukuoka marathons last year, is cautious, however, about committing to the marathon at this summer's World Championships in Japan.
Gebrselassie runs successful construction and restaurant operations in the Ethiopian capital of Addis Ababa, as well as building schools.
He says it would be difficult to spend time away from his family and business in order to train specifically for the humid conditions in Osaka.
"It's difficult for me to be away from home," said Gebrselassie. "These days, after training I have to go straight into the office and see what is going on - it is an enormous responsibility.
"It would be very hard for me to run Osaka and because of that I've not decided yet."
Stefano Baldini, the reigning Olympic and European marathon champion, may also opt out of the marathon at the Worlds.
The 35-year-old Italian, who has completed 13 marathons under two hours 10 minutes, also revealed he would retire after attempting to defend his Olympic title in 2008.
"My career is very long and I want to close it in style," Baldini said.
"I want to finish at a major championships, I am the defending champion and so it will be a good way to end in Beijing. I am saving all my energy for next year."
Gebrselassie and Baldini are amongst the strongest line-up to contest the London Marathon in some years.
World record holder Tergat finished second in London in 2000 and 2001
The duo face leading contenders world-record holder Paul Tergat, double world champion Jaouad Gharib, defending champion Felix Limo, 2005 winner Martin Lel and, surprise winner of the New York Marathon, Marilson Gomes dos Santos.
Conditions are expected to be good in London, though with temperatures forecast at 20C, a little gruelling over 26.2 miles.
Amidst such a quality field Tergat, who holds the world record of 2:04.55, says it will be difficult to pick out a favourite for London.
"This is one of the high-class events in the world and anything could happen," Tergat told BBC Sport.
"I'm expecting somebody to break mid-way through the race, otherwise if it is tactical even the best runners could lose to somebody else.
"It will be really fast too, between 2:06 and 2:07 would be a good time."
As well as being in the mix for the title, Gebrselassie is on a personal mission to improve on his performance in London last year.
The Ethiopian, who came third on his debut in 2002, finished ninth and described it as, "the worst race of his career".
He said: "Since I started running I've never been in ninth place, my worst finish was in 1991 when I finished eighth in a junior race.
"It is no question how important it is to win in London, it is absolutely the number one marathon.
"If I win just once in London I will feel as if I've just won at the World Championships."