Officials deny that the programme is dead but say that it is under review. Earlier this year the Department of Energy predicted a $6.6 billion cost for conversion of the American stocks to fuel, about three times the initial estimates. It put Russia’s cost at $1.76 billion.

The plan, conceived in the mid-90s, was to take 50t each of American and Russian plutonium from weapons and either convert into MOX fuel or immobilise by mixing with nuclear waste. The Clinton administration expected that the US and other rich countries would help pay, but no firm pledges were ever made.

The proposed DoE budget does not include the money needed for immobilisation. Conversion to MOX also looks unlikely – there are no facilities in the US or Russia at present, and no firm plans to build any.

The Bush administration appears to be considering a variety of other options, including a new generation of reactors that could burn plutonium more thoroughly.