KIEV, March 11 (Xinhua) -- Ukraine issued an appeal to the Budapest Memorandum guarantor countries Tuesday for assistance to preserve its territorial integrity.
In the appeal, approved by the Ukrainian parliament, Kiev asked the United States and Britain to "apply all possible diplomatic, political, economic and military measures" to maintain Ukraine's independence and sovereignty.
In 1994, Kiev signed the Budapest Memorandum, under which Ukraine gave up its nuclear weapons in exchange for a guarantee of recognition of its sovereignty.
Russia, the United States and Britain, as guarantors of the treaty, are obliged not to use force against Kiev and mediate if a threat to Ukraine's territorial integrity arises.
Ukraine now faces the threat of splitting up, after the parliament of its southern region, the Autonomous Republic of Crimea, adopted a declaration of independence from Ukraine Tuesday.
That decision will now be put to Crimean voters for approval in a referendum on Sunday.
Since the outbreak of the Crimea crisis in late February, Kiev has been accusing Moscow of exacerbating the situation by increasing troops in Crimea, which is home to Russia's Black Sea Fleet.
Crimean Parliament Speaker Vladimir Konstantinov said Tuesday the autonomous peninsula became a parliamentary republic after Crimean lawmakers adopted the declaration of independence.
"By adopting the declaration, we have stated ourselves as a republic," Konstantinov said, adding Crimea was "not a Ukrainian autonomous region any more."
The declaration was needed for judicial procedures as a part of Crimea's entry to Russia, said Konstantinov, emphasizing Crimea "will not return to Ukraine."
To come into force, the parliament's decision must be confirmed by the March 16 referendum over the future status of the peninsula.
Kiev has described the referendum as "illegal," saying it violates the legal procedures established by the Constitution of Ukraine.
The Crimean peninsula was transferred to Ukraine in 1954 as a gift to Kiev by then Soviet leader Nikita Khrushchev to mark the 300th anniversary of Ukraine's merger with the Russian empire.