The International Space Station [Images] faces an uncertain future with the United States making it clear that it will not support the orbital outpost beyond 2015. On the other hand, key ISS partners Russia [Images] and the European Space Agency have announced that they will not be able to fund the project on their own and may abandon it if the US backs out.

This has put a question mark on future ISS projects and has put space agencies in a dilemma about accepting research proposals for the station. The US has told ISS partners that its space agency has no plans to use the orbital research lab for more than five years after its completion in 2010, ESA Director-General Jean Jacques Dordain said on the sidelines of the International Astronautical Congress in Hyderabad on Wednesday.

"If NASA [Images] is staying, we are ready to follow. If NASA is quitting, I shall not propose to ESA to pay part of the cost that NASA is covering today," he said. The US space agency has projected its own annual bill for the project to reach US $2.3 billion by 2010 while Dordain said that the ESA would be paying approximately US $1.5 billion.

"It will not be feasible for us to maintain the space station," said General Anatoly Perminov, head of the Federal Space Agency, Russia. The ISS, a joint venture between the US, Europe, Russia, Japan [Images] and Canada [Images], is being assembled at an altitude of 350 kms above the surface of the earth.

Perminov was quick to add that there was no official announcement by the US about quitting the ISS. "Till such an official announcement is made, it is a joint programme between the participating nations," he said.

The station has been inhabited since the first crew entered it in November 2000, providing a permanent human presence in space. It has been visited by space tourists as well as astronauts. There have been suggestions to use the ISS for research to plan future inter-planetary travel including round-trip manned missions to the moon and Mars [Images].