The Kremlin has also accused Ukraine of supplying Georgia with arms that were used during the country's assault on South Ossetia last August.

The letter was accompanied by Moscow’s delaying of the departure for Kiev of Russia’s new ambassador to Ukraine. Medvedev said that it will only happen once relations improve.

Viktor Yushchenko said any arms delivered to Georgia were in compliance with international law and added that Moscow's decision to delay its new ambassador's arrival to Ukraine would not help cooperation between the two countries.

President Yushchenko also said he was very disappointed by the Russian leader's “unfriendly” letter.

Meanwhile, Ukrainian Prime Minister Yulia Timoshenko said the country was pursuing its own political interests which should not be regarded as a policy directed against Russia, or any other country for that matter.

She added that, while Ukraine’s policies would remain independent, the interests of the country’s partners would always be taken into account.

Timoshenko also stated that any standstill in relations with Russia was “impermissible”.

However, even under the current circumstances, some experts believe the current stand-off could benefit both countries.

“What is going on now is rather more positive than negative, because it is quite obvious that for a long period of time there were many contradictions that waited for resolution. And now we have such a moment when the Russian leadership, as well as the Ukrainian leadership for sure, will come to a new quality, to a new position in the debates over Ukrainian and Russian mutual politics. In my view there is nothing dramatic in what is going on because there’s space for friendly and constructive relations between Russia and Ukraine,” said Mikhail Dmitriev from Moscow State University’s Ukrainian Studies Center.

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