Ukraine's parliament has renounced the country's non-aligned status with the aim of eventually joining NATO, angering Moscow which views the Western alliance's eastward expansion as a threat to its own security.
Introducing the bill on Tuesday, former prime minister Yulia Tymoshenko said it was a vital bill for Ukraine in current times.
"Today we all should vote for a key bill in the current situation - a bill about peace, a bill about the reform strategy, a bill about our place in the Western civilisation. This is a bill denouncing Ukraine's "non-aligned" status," said Tymoshenko.
Kiev first announced its intention of seeking the protection of NATO membership in August following what it deemed the open participation of Russia's military in a separatist war in Ukraine's eastern provinces.
Non-aligned statuses are a classification given to states such as Switzerland which refuse to join military alliances and thus play no part in wars.
The amendment passed easily in parliament, receiving 303 votes, 77 more than the minimum required to pass into law.
Russian Foreign Minister Sergei Lavrov called Ukraine's renunciation of its neutral military and political status a "counterproductive" step that would only boost tensions around the crisis in the east.
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"It will only escalate the confrontation and creates the illusion that it is possible to resolve Ukraine's deep internal crisis by passing such laws," TASS news agency quoted Lavrov as saying.
Ties between Moscow and Kiev are at an all-time low since Russia's annexation of the Crimean peninsula from Ukraine in March and the subsequent outbreak of the pro-Russian rebellion in the east.
Pro-Western authorities in Kiev accuse Russia of orchestrating and arming an uprising after the overthrow of a Ukrainian president sympathetic to Moscow. The Kremlin denies that it is behind the revolt.
Any accession to the Western military alliance is likely to take years, but a NATO spokesman in Brussels said: "Our door is open and Ukraine will become a member of NATO if it so requests and fulfils the standards and adheres to the necessary principles."