There will be no war between Russia and Ukraine, the speaker of Russia's upper house of parliament said on Friday.
"It's complete nonsense, it absolutely does not reflect our intentions, the feelings of empathy and the pain we feel for the Ukrainian people," said Valentina Matviyenko, head of the Russian Federation Council.
"We are absolutely sure that there will never be a war between the two brotherly nations."
Crimea's parliament has the right to hold a referendum on the region's future status, the speaker of Russia's upper house of parliament said on Friday.
The parliament in Ukraine's southern Crimea region said on Thursday it would hold a referendum on whether the region should join Russia on March 16.
"Yesterday we learned about the historic decision taken by the Crimean parliament to hold a referendum on accession, on entry into the Russian Federation," said Valentina Matviyenko, head of the Russian Federation Council.
"Without a doubt, the Crimean parliament, as a legitimate authority, has that right ... The sovereign right of the people to determine their future."
President Vladimir Putin rebuffed a warning from US President Barack Obama over Moscow's military intervention in Crimea, saying on Friday that Russia could not ignore calls for help from Russian speakers in Ukraine.
After an hour-long telephone call, Putin said in a statement that Moscow and Washington were still far apart on the situation in the former Soviet republic, where he said the new authorities had taken "absolutely illegitimate decisions on the eastern, southeastern and Crimea regions.
"Russia cannot ignore calls for help and it acts accordingly, in full compliance with international law," Putin said.
The most serious east-west confrontation since the end of the Cold War escalated on Thursday when Crimea's parliament, dominated by ethnic Russians, voted to join Russia. The region's government set a referendum for March 16 - in just nine days' time.
European Union leaders and Obama denounced the proposed referendum as illegitimate, saying it would violate Ukraine's constitution.
Before calling Putin, Obama announced the first sanctions against Russia since the start of the crisis, ordering visa bans and asset freezes against so far unidentified persons deemed responsible for threatening Ukraine's sovereignty.
Japan endorsed the Western position that Russia's actions constitute "a threat to international peace and security" on the crisis after Obama spoke to Prime Minister Shinzo Abe.
The EU, Russia's biggest economic partner and energy customer, adopted a three-stage plan to try to force a negotiated solution but stopped short of immediate sanctions.
Brussels and Washington also rushed to strengthen the new authorities in economically shattered Ukraine, announcing both political and financial assistance.
In their telephone call, Obama said he urged Putin to accept the terms of a potential diplomatic solution, and said the dispute over Crimea could be resolved in a way that took account of Russia's legitimate interests in the region.
Putin was defiant on Ukraine, where he said pro-Russian President Viktor Yanukovich had been overthrown in an "anti-constitutional coup" last month. But he stressed what he called "the paramount important of Russian-American relations to ensure stability and security in the world", the Kremlin said.
"These relations should not be sacrificed for individual differences, albeit very important ones, over international problems," Putin said.
He maintained Moscow was not behind the seizure of Crimea, home of Russia's Black Sea Fleet. Russia says the troops without national insignia that have surround Ukrainian bases are "local self-defense units". The West has ridiculed this argument.
After talks in Rome on Thursday, US Secretary of State John Kerry said Russian Foreign Minister Sergei Lavrov was personally delivering proposals to Putin to end the crisis.
Kerry said the executive order signed by Obama on Thursday provided a legal framework for imposing sanctions but also left open the door for dialogue.
The 28-nation EU welcomed Ukrainian Prime Minister Arseny Yatseniuk to its emergency summit, even though Kiev is neither a member nor a recognized candidate to join the bloc, and agreed to bring forward the signing of the political parts of an agreement on closer ties before Ukraine's May 25 elections.
"No one will give up Crimea to anyone," Yatseniuk told a news conference in Brussels, while Ukraine's acting president, Oleksander Turchinov, called the planned referendum "a farce, a fake, a crime".
The European Commission said Ukraine could receive up to 11 billion euros ($15 billion) in the next couple of years provided it reaches agreement with the International Monetary Fund, which requires painful economic reforms like ending gas subsidies.