Russia has threatened to target the Ukraine with nuclear warheads if the former Soviet republic joins Nato and accepts the deployment of United States anti-missile defences on its territory.

President Vladimir Putin of Russia warned Viktor Yushchenko, Ukraine's leader, of "retaliatory actions'' should his country join the Western alliance.

"It's frightening not just to talk about this, but even to think about, that in response to such deployment, the possibility of such deployments -- and one can't theoretically exclude these deployments -- that Russia will have to point its warheads at Ukrainian territory,'' he said during a joint press conference in Moscow. The Russian and Ukrainian leaders had just held emergency talks in the Kremlin to avert a energy supply crisis over Kiev's gas bill -- a similar dispute two years ago led to power cuts across Europe.

Mr Yushchenko responded to the Russian pressure by insisting on Ukraine's right to decide its own foreign policy while stressing that his country's constitution would not allow US military bases on its territory.

Mr Putin has condemned Washington's plans to include Poland and the Czech Republic in a missile defence shield as a "new phase in the arms race''.

Russia fears the shield will threaten its national security and tip the strategic military balance in Europe.

Moscow has already declared that Russia will pull out of the Conventional Forces in Europe Treaty (CFE), which came into force in 1992 and restricts the deployment of troops near sensitive European frontiers.

Warning

Last week, John Chipman, the head of the International Institute for Strategic Studies, gave warning that the "next target of Moscow's assertive revisionism'' could be the Intermediate Nuclear Forces (INF) Treaty of 1987.

Both moves would allow Russia to build a new generation of medium-range nuclear missiles capable of striking Western Europe. Ukraine's membership request to Nato will be considered at a summit in the Romanian capital of Bucharest in April. Mr Putin has accepted an invitation to attend.

The prospect of Nato membership is controversial in the Ukraine, where opinion polls show more than half of the country opposes it.

Russia has revived the long-range air patrols that were a feature of the Cold War and US defence officials confirmed that a pair of Russian TU-95 Bear bombers flew at 2,000 feet over the US aircraft carrier Nimitz in the western Pacific at the weekend. (© Daily Telegraph, London)