Ukrainian Prime Minister Yulia Tymoshenko said yesterday a lease agreement for the Russian Black Sea fleet's Sevastopol base should not be renewed after it runs out in 2017.
Russia, which has had a fleet in Sevastopol for 225 years, wants to extend the lease. A senior Russian naval officer said earlier this month the port was geographically by far the best option for Moscow in the Black Sea.
"We need to fulfil this agreement until 2017, as it was signed by the two sides. After that, we need Ukraine to be a zone free of military bases. This is our precise position and we will hold to it," Ms Tymoshenko told reporters. She had previously said no "radical" decisions should be taken on the lease.
Ukraine backed Georgia in its brief conflict with Russia last month and was angered when Moscow deployed ships from Sevastopol. Tensions rose at the end of last month when Ukrainian President Viktor Yushchenko tightened the rules for the movement of the fleet. Ukraine's ruling coalition in Parliament fell apart this month after the departure of Yushchenko's Our Ukraine party, junior partner in the alliance.
If the coalition cannot be rebuilt or an alternative found, Mr Yushchenko can call an election, which would be the third parliamentary poll in as many years.
Mr Yushchenko's supporters have accused Ms Tymoshenko of betraying Ukraine by failing to condemn Russia's intervention in Georgia.
Ms Tymoshenko, who has expressed support for Georgia's territorial integrity, has in turn said Mr Yushchenko's strident tone has spoiled relations with the Kremlin.
Sevastopol is located in the Crimean peninsula, which became part of Russia in the late 18th century. It was handed to the Ukrainian Soviet Socialist Republic in 1954 when the collapse of Soviet rule was unthinkable.
Meanwhile Ukrainian President Viktor Yushchenko vowed yesterday his country would be undeterred in its bid for Nato membership despite Russian opposition.
Mr Yushchenko reaffirmed his pro-Western government's Nato aspirations in a speech to the UN just weeks after Russia's military incursion in Georgia sparked international condemnation and stirred concerns in Ukraine and other former Soviet republics.
"Ukraine rejects pressure of any kind regarding ways to ensure its own security and to determine membership in collective security structures," he told the annual General Assembly gathering of world leaders. "Such attempts of infringement are short-sighted and counterproductive."
Mr Yushchenko was referring to US-backed efforts by Ukraine, along with Georgia, to join Nato, a drive that has incensed Moscow. He did not specifically name Russia.
Nato leaders at their April summit stopped short of putting Ukraine and Georgia immediately on the path to membership in the alliance but pledged the two ex-Soviet states would one day become members.