Kasyanov told a cabinet meeting in televised remarks that the extra cash would have to be funneled from both budgetary funds and other reserves.

His comments came one day after Russian space agency chief Yury Koptev warned the ISS would have to be mothballed next year unless Russia receives additional foreign financing.

Forty astronauts were to have visited the ISS in 2003, onboard two Russian Soyuz rockets and five US shuttles, with three Russian Progress cargo craft delivering supplies.

But after the Columbia space shuttle disintegrated on February 1 as it returned to Earth from a mission, NASA ground its shuttle program. Russia's manned Soyuz and cargo Progress craft are now the only way for transporting crew and supplying the ISS.

Kasyanov was quoted as telling his government that ways to find extra financing "demands an urgent decision" from the Russian cabinet.

"We have to analyze the situation and make forecasts, in order for this project to go ahead."

Russia has said it needs at least another 50 million dollars for space flights.

Moscow had taken on an obligation to fly two manned Soyuz flights and five unmanned Progress cargo craft to the ISS this year. Water and food supplies were mainly delivered by US shuttles.

The Russian government decided earlier this year to spend the entire year's space budget funds during the first six months and then seek extra financing from Washington or European partners in the 16-nation ISS.

But Washington has indicated it would not provide the funds as the Iran Nonproliferation Act (INA) prohibits US funding for the Russian space program because of Moscow's nuclear and other military cooperation with Tehran.

No European partner has agreed to provide funds.

A US-Russian crew is tentatively scheduled to blast off for the ISS on board a Soyuz craft on April 26.

SPACE.WIRE