With the first components of the international space station just over 100 days away from launch Nasa's decision will hurt Russian pride.

Nasa says it is necessary to save the project.

Space shuttle to be modified

Russia was expected to provide more than 40 missions to resupply and boost the orbit of the the space station.

But it has been clear for a while that the country will not be able to afford all of them.

To compensate Nasa will modify the steering thrusters on its four space shuttles so when the shuttle visits the space station it can boost it into a higher orbit.

The space station's orbit will constantly decay because of atmospheric drag. Reboosts are required to prevent it from burning up in the atmosphere.

Nasa is also considering building a brand new spacecraft to serve as an onboard booster.

The modifications to the space shuttle are part of a contingency plan that will reduce Russia's contribution in the project.

Costs are spiralling

The cost of the space station is in danger of going into orbit. When it was redesigned in 1993, Nasa predicted it would cost $17bn.

Now the cost has spiralled to at least $25bn.

It may get worse. The much-delayed Russian Service Module, which will provide living quarters during the station's early phases, might not be ready for an April 1999 launch.