Griffin, speaking to journalists at the Paris Air Show here, said he would hold talks with his counterparts from Canada, Europe, Japan and Russia, starting this week, about revising the schedule to build mankind's orbit in space.

"Over the course of this summer we will be refining the plan by which we are going to complete the development of the space station," he said, adding that he hoped the plan would be finished by October.

The 60-billion-dollar ISS was badly hit by the loss of the US space shuttle Columbia on February 1, 2003.

The shuttle is the only heavy lifter for bringing up from Earth large modules that are then assembled in orbit. Without it, the only available craft are much smaller Russian unmanned freighters. Since the loss of Columbia, the ISS has been manned by just a skeleton crew.

Flights by the remaining three US shuttles are due to resume in the coming months after a long period of safety assessments and revisions by NASA engineers.

But Griffin said it would be impossible for the three craft to carry out all 28 remaining missions needed to complete the ISS by the time they are withdrawn from service in 2010.

"That is not a plan that we can execute, and so we need a better plan," Griffin said.

"We have best-case, worst-case and average-case flight rates with the shuttle. I should say we should easily be able to do more than 15 but we know that it is beyond reason to expect to be able to do 28 shuttle flights by 2010," Griffin said.

The United States is shouldering the lion's share of the ISS, a project whose first modules were assembled in 1998.

The US partners in the scheme have looked on in dismay as the ambitious construction programme first fell behind schedule and then was put on hold after the loss of Columbia.

Their worry is that some of the billions of dollars that they have invested in building modules for the ISS and training astronauts for scientific work in orbit will be wasted.

Some units may never be added to the ISS or if they are, their full scientific value may never be realised because the station will be operated by just a minimum crew, they fear.

Griffin said: "It is our intention to launch the Columbus (science) module and all the international partner modules. We have obligations to the space station partnership and we take that seriously."

Asked as to what the revised launch and construction programme would look like, he said, "We are looking at other possibilities, other launch vehicles, delays, various possibilities."

All rights reserved. copyright 2018 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.