Energy Secretary Bill Richardson is hoping for a quick solution to the problems surrounding Washington’s agreement to buy 500 tons of highly enriched uranium (HEU) from decommissioned Russian nuclear warheads to fuel commercial nuclear power reactors.

“There are still some issues we need to narrow down,” he told a conference sponsored by the Carnegie Endowment for International Peace.

Under the $12 billion 1993 deal, Russia was to convert 500 t of HEU into low-enriched uranium (LEU) over 20 years and send it to the US after dilution. The US originally agreed to pay for both natural and enriched components but at the end of 1996 it stopped paying for the uranium’s natural component. Instead it said it was willing only to pay for the enriched part, and for the natural component it has been returning an equal amount of natural uranium. Russian energy officials accused Washington of violating its obligations and said they would begin selling the natural uranium on world markets.

The situation was complicated when the United States Enrichment Corp, Russia’s partner in the 1993 deal, was privatised last year and when Russia put a value on the uranium out of line with world prices. Richardson said that under the deal, 36 tons of Russian HEU – enough for over 2500 nuclear weapons – has been blended down and delivered to the US .