Ukraine threatened to blockade the Russian Black Sea Fleet yesterday in an act of solidarity with Georgia that risked escalating the conflict.

After flying to Tbilisi to assure Georgians of his country’s support, President Yushchenko signed an order imposing tough restrictions on the Russian fleet, which is based in the Ukrainian port of Sevastopol. Mr Yushchenko’s decree instructs Russia to give 72 hours’ notice of any movement of ships, aircraft or personnel in Ukraine. The Ukrainian authorities were given the power to alter those plans.

The Ukrainian Foreign Ministry had already warned Russia that it will bar ships from returning to Sevastopol if they take part in military action against Georgia. Moscow responded furiously, accusing Ukraine of a “serious new antiRussian step”.

Like Georgia, Ukraine’s pro-Western leadership is seeking membership of Nato in December. The democratic Orange Revolution that swept Mr Yushchenko and Yuliya Tymoshenko, the Prime Minister, to power in 2004 has long been loathed by Vladimir Putin, the Russian Prime Minister.

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The Ukrainian Security Council issued a statement yesterday declaring that the presence of foreign warships in its waters “poses a potential threat to Ukraine’s national security, particularly if parts of Russia’s Black Sea Fleet are used against third countries”.

Russia and Ukraine are already at loggerheads over the future of the Crimean base, which Russia must vacate in 2017 under a 20-year lease agreement signed after the collapse of the Soviet Union. Most of Crimea’s population consider themselves to be Russians and are strongly pro-Moscow. Tensions have mounted over calls by politicians in Moscow not to surrender control of the territory, regardless of Ukraine’s wishes. Mr Yushchenko insists that the Black Sea Fleet must leave on time and that there is no prospect of extending the lease.

Ukraine’s ambition for Nato membership has raised tensions still further. Russia is opposed to the Western military alliance replacing it in Crimea and Mr Putin has threatened to target nuclear missiles at Ukraine if it joins Nato.Unlike tiny Georgia, Ukraine is a country of 47 million people and any confrontation with Russia could quickly escalate into a broader European conflict. Vital Russian gas pipelines cross Ukraine to supply the European Union.

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