General Vladimir Yakovlev, commander of Russia's missile force, has insisted that a new generation of such defences will have dire consequences for arms control.

The Pentagon is currently testing a system intended to destroy incoming long-range missiles - known as an Exoatmospheric Kill Vehicle.

A target missile was successully destroyed in recent US trials

Russia has greeted the work with dismay, arguing that the finished weapon would breach the 1972 Anti-Ballistic Missile (ABM) treaty.

The agreement has long been viewed as the bedrock of nuclear arms limitation.

The Russian First Deputy Defence Minister Nikolai Mikhailov has already said his nation's nuclear arsenal would be improved to counter any treaty violation.

The US claims its system is intended to counter a limited attack by a rogue state, such as Iraq or North Korea, and not a sustained barrage from Russia.

Deterrent undermined

Fearing that its entire nuclear deterrent would be undermined, Russia has resisted US calls to modify the ABM treaty.

General Yakovlev also announced that Russia had tested its existing ABM system - which falls within treaty requirements - for the first time since 1993.

Russia fears another arms race

Although he said the firing proved Russia's ABM defence was still operational, experts have questioned the system's effectiveness.

It is believed that Moscow's anti-ballistic missile shield is crumbling and that the government cannot fund a new system to match that of the US.

The Pentagon is also working on the Theatre High Altitude Area Defence (THAAD) weapon - a defence against medium-range missiles.

Last week, US Secretary of State Madeleine Albright said she was "troubled" by Russia's stance on the ABM treaty.

Calming fears

The US has reportedly offered to complete a half-built radar defence site in Russia and share early-warning data to help allay fears in Moscow.

Many nations are developing long-range missiles

However, General Yakovlev's comments are the most direct evidence so far of Russia's continuing concern at ABM research.

The issue promises to sour US-Russia relations as both countries head towards presidential elections.

The expansion of ABM cover has received the backing of many Republican candidates in the US, particularly since the firing of a North Korean missile into the Pacific last year.