Crimea is expected to formally apply to join Russia after voting to split from Ukraine as Europe prepared to hit Moscow with a wave of sanctions in the worst East-West standoff since the Cold War.
Russia's lower house of parliament will pass legislation allowing Crimea to join Russia in "the very near future," the house's deputy speaker was quoted by Reuters news agency as saying on Monday.
The head of the referendum commission in Ukraine's Crimea says the final results of the Sunday vote show that 97 percent of voters have supported joining Russia.
Mikhail Malyshev said in a televised news conference on Monday that the final tally was 96.8 percent in favour of splitting from Ukraine.
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Crimea's regional assembly will meet early on Monday to apply to merge with Russia, a process that could take months and is mired in uncertainty for a region that remains heavily dependent on the Ukraine mainland.
There was sharp international condemnation of the vote, which could see the most radical redrawing of the map of Europe since Kosovo's 2008 declaration of independence from Serbia.
The European Union said the referendum was "illegal and illegitimate" and its outcome would not be recognised.
In Brussels on Monday, European foreign ministers are expected to unfurl sanctions including visa bans and asset freezes against leading figures in Moscow. However, members of the Russian government are not expected to be affected.
US President Barack Obama has told Russian President Vladimir Putin that Crimea's vote to secede from Ukraine and join Russia "would never be recognised" by the United States, as he and other top US officials warned Moscow against making further military moves towards southern and eastern Ukraine.
The White House said Obama reminded Putin over the phone that the US and its allies in Europe would impose sanctions against Russia should it annex Crimea.
Putin maintained that the vote was legal and consistent with the right of self-determination, according to the Kremlin.
In the call, Obama urged Putin to pursue a diplomatic de-escalation of the crisis, support the Ukraine government's plans for political reform, return its troops in Crimea to their bases, and halt advances into Ukrainian territory.
Obama told Putin that "a diplomatic resolution cannot be achieved while Russian military forces continue their incursions into Ukrainian territory and that the large-scale Russian military exercises on Ukraine's borders only exacerbate the tension," the White House said in a statement.
Russia, meanwhile, maintains the acting government in Kiev is illegitimate and says it seized power in a "coup".
With no military response envisioned, and with US and EU sanctions apparently foregone conclusions, the Obama administration slightly shifted its focus to keeping Russia from encroachment into Ukraine beyond Crimea, where it has a large naval base.