NEW YORK (AFP) - Uranium fuel from 20,000 disarmed Russian warheads is now generating about half of US nuclear power in a spin-off from a landmark disarmament accord, a top US official said on Wednesday.

Ms Rose Gottemoeller, US undersecretary of state for arms control, told a UN committee a 1993 accord between the two former Cold War rivals was one of a growing list of disarmament successes.

The final uranium delivery of uranium that the United States buys from Russia is due to leave St Petersburg next month, Ms Gottemoeller told the UN disarmament committee. She hailed the accord as a "significant non-proliferation accomplishment", adding 500 tonnes of weapons-grade uranium has now been processed in Russia.

Low enriched uranium left from the downgrading "is delivered to the United States, fabricated into nuclear fuel and used by nearly all US nuclear power plants to generate half of the nuclear energy in the United States", she disclosed.

"Approximately 20,000 nuclear warheads have been eliminated under this unique government-industry partnership," Ms Gottemoeller told the UN committee.

Over the past 15 years the Russian uranium fuel has accounted for about 10 per cent of electricity produced in the US, she added.

US officials will go to St Petersburg next month to mark the loading of the final containers which should arrive in the US in December, Ms Gottemoeller said.

"We look forward to celebrating this historic achievement," she said.