A senior Russian military official, Leonid Ivashov, said the Americans wanted changes to be made to the 1972 Anti-Ballistic Missile treaty (ABM) to allow them to develop a regional anti-missile system.

Mr Ivashov said the Americans had handed out research contracts for the system before consulting Moscow.

Regional shield

Russia and the United States have completed three days of talks on the American proposal to modify the ABM and on further cuts to each other's nuclear arsenal.

Leonid Ivashov: Critical of the US plan

But Mr Ivashov said talks with the Americans had not changed Moscow's opposition to amending the ABM, and had produced no results on possible new nuclear weapons reductions.

"The ABM treaty is the basis on which all subsequent arms controls agreements have been built. To destroy this would be to destroy the entire process of nuclear arms control," Mr Ivashov said.

The US wants the ABM changed to allow it to build a regional missile defence system in the face of threats from "rogue states" such as North Korea and Iran.

Washington argues that the plan would not upset the military balance, since the system would not be effective against the Russian missile arsenal.

Arms race

But Russia strongly opposes any changes, fearing it would alter the existing strategic balance.

The head of the Russian delegation to the talks, Grigory Berdinnikov, told reporters it could affect the entire arms control framework.

Yeltsin signed Start-II with Clinton in 1993

"We do not see any variant which would allow the US to deploy a national anti-missile defence system and at the same time maintain the ABM treaty," Mr Berdinnikov said.

He warned that if the US went ahead with its plans the arms race could "leap to outer space".

Presidents Bill Clinton and Boris Yeltsin signed the Start-II treaty in 1993, to reduce their nuclear stockpile from existing levels to 3,500 warheads by 2003.

The treaty was ratified by the US Senate in 1996 but has yet to be passed by the Duma, the Russian lower house of parliament.

The US wants the Russian parliament to ratify the treaty before it negotiates the Start-III, which would cut warheads to around 2,000 on each side.