Nasa is talking to Japan's space agency about using one of its spacecraft for servicing missions to the International Space Station, according to Japanese media reports.

Nasa has been considering various options to maintain its commitment to the Space Station after the Space Shuttle is retired from service in 2010.

Discussions between Nasa and the Japan Aerospace Exploration Agency (Jaxa) were described as "unofficial negotiations" by daily newspaper Yomiuri Shimbun.

The paper did not identify the source of its information, but said that the negotiations began in February.

Jaxa's 10-metre H-2 transfer vehicle can lift up to six tonnes of cargo into orbit, and is being designed and built in Japan by Jaxa, Mitsubishi and other contractors.

The first launch is expected next year on Japan's H-2B rocket, which is also under development.

Currently, Jaxa plans to launch one H-2 per year, carrying scientific experiments as it tests and develops the project. Each transfer vehicle costs approximately $131m, according to press reports.

The International Space Station requires regular supplies of food, water, oxygen and equipment.

While Russia offers the only viable alternative method of regularly transporting astronauts into space, there are several countries with the ability to launch non-human cargo, including Japan, the European Space Agency and China.

The ESA recently carried out the first successful test flight of its cargo carrying an automated transfer vehicle to the Space Station.