Organisers of the five big city marathons are planning to launch a Grand Slam format with a special bonus for any athlete who wins the London [Images], New York City, Boston, Chicago and Berlin races.

"I can confirm there have been discussions but there's nothing in place yet," London race director Dave Bedford said. "I would prefer not to comment any further at the moment."

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Sources close to another of the big marathons said the five race directors had met at St Etienne in France [Images] last month during the world cross country championships to discuss closer co-operation. They said a Grand Slam proposal was likely to be announced during the world athletics championships in Helsinki this August.

New York race director Mary Wittenberg said all the race directors are in constant contact.

"We see the opportunity to take the sport to a new level," she said. "And we all want the title of the world's best marathon.

"We have the opportunity to look beyond ourselves. We look at other sports, we look at soccer, we look at NASCAR. We see the benefit some of the major sports organisations have derived from being much more than single events."

Wittenberg said history, tradition and media coverage had led to the four majors in golf and the four Grand Slam tournaments in tennis.

"They have four in a year, that's not what we have," she said. "We have to be more creative."

Wittenberg would not comment directly on the prospect of a Grand Slam, which because of the special demands of marathon running would not be completed within a calendar year.

"We are just talking about a lot of things," she said. "About how we can make this more compelling. How do we get the stars? Let's cultivate the next Paula [Radcliffe], the next Haile [Gebrselassie]. We don't have Tiger Woods [Images] in the sport so we are constantly looking at that."

Norwegian Ingrid Kristiansen, the only person to win in London, New York, Chicago and Boston, welcomed the idea.

"It would be nice," she said. "I think it's a smart idea. All the best runners could go for all the races."

International Association of Athletics Federations (IAAF) spokesman Nick Davies, who was also present at Sunday's London marathon in which 35,680 people competed, said big city marathons are now a social phenomenon.

He said the IAAF would be interested in anything which helped promote the sport, including a possible link between the biennial world championships marathon and the big city quintet.

Sunday's women's race was won for the third time by Radcliffe, who has also recorded victories in Chicago and New York. She appears certain to defend her New York title in November but as she wants to keep running through the 2008 Beijing [Images] Olympics [Images] there would be plenty of opportunities over the next few years to run in Boston and Berlin.