Ukraine's parliament has voted to abandon the country's neutral "non-bloc" status and set a course for NATO membership, a move immediately denounced by Russia as "unfriendly."
The legislative amendment submitted by President Petro Poroshenko last week was approved with 303 "yes" votes in the 450-seat Verkhovna Rada on December 23.
A note explaining the changes in Ukraine's law on domestic and foreign policy said that the "non-bloc" status codified under then-President Viktor Yanukovych in 2010 had left Ukraine vulnerable to "external aggression and pressure."
It said that "the Russian Federation's aggression against Ukraine, its illegal annexation of Crimea...its military intervention in eastern regions" and other forms of pressure created the need for "more effective guarantees of independence, sovereignty, security, and territorial integrity."
The pro-Western leaders who came to power after Yanukovych fled in the face of protests last February have spoken for months of plans to renounce the neutral status, which prevented Ukraine from seeking NATO membership.
Kyiv and NATO accuse Russia of providing direct military support to pro-Russian separatists who have seized parts of two provinces in eastern Ukraine and fought government forces in a conflict that has killed more than 4,700 people since April.
"Ukraine's fight for its independence, territorial integrity, and sovereignty has turned into a decisive factor in our relations with the world," Poroshenko told foreign ambassadors in Kyiv late on December 22.
Before the vote, former Ukrainian Prime Minister Yulia Tymoshenko described the legislation to fellow lawmaker as "a bill about our place in Western civilization."
The legislation approved by parliament says Ukraine will tighten cooperation with NATO with the aim of "achieving the criteria required to attain membership" in the Western military alliance.
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."
The White House said it supported NATO's open-door policy.
"The United States supports the right of Ukrainians to make their own decisions about the future of their country free from any outside interference," a senior administration official said.
Russia's envoy to the OSCE, Andrei Kelin, called the legislation "unfriendly" and said it would "add trouble and tension to our relationship."
Russian Foreign Minister Sergei Lavrov said it was a "counterproductive" move that "escalates confrontations and creates the illusion that the profound internal crisis in Ukraine can be resolved through the adoption of such laws."
And the Russian permanent representative to NATO, Aleksandr Grushko, said the Ukrainian vote creates "serious complications in the search for a way to end the violence and change the situation into a political process."
In a Facebook post early on December 23, before the vote, Russian Prime Minister Dmitry Medvedev said the legislation to abandon nonaligned status was "in essence, an application to enter NATO, turning Ukraine into a potential military opponent of Russia."
Moscow has frequently warned that it strongly opposes Ukrainian membership in NATO and has called for formal assurances that this will never happen.
President Vladimir Putin has suggested that the main reason Russia annexed Crimea from Ukraine in March was the prospect of NATO forces being deployed on the peninsula.
Russia used troops and a referendum denounced abroad as illegal to annex Crimea after Yanukovych was driven from power by protests over his decision to scrap plans for a landmark treaty with the EU and tighten ties with Moscow.
The vote in Ukraine added to tension ahead of a planned new round of talks -- involving representatives of Ukraine, Russia, the rebels, and the OSCE -- aimed to end to the conflict in eastern Ukraine.
After a four-way telephone call between Poroshenko, Putin, German Chancellor Angela Merkel, and French President Francois Hollande, Poroshenko's office said the negotiations will be held in the Belarusian capital, Minsk, on December 24 and 26.
More than 1,000 people have been killed in eastern Ukraine despite a September 5 deal on a cease-fire and steps toward peace, but fighting has abated this month.