Valentina Matvienko, the speaker of Russia's upper house of parliament, said the country would welcome Crimea if it votes in the referendum to join its neighbour.
"If the decision is made, then Crimea will become an absolutely equal subject of the Russian Federation," Ms Matvienko said during a visit from the Crimean prime minister, Sergei Aksyonov, and chairman of the Crimean parliament Vladimir Konstantinov.
The strategic peninsula has become the flashpoint in the battle for Ukraine, where three months of protests sent President Viktor Yanukovych fleeing to Russia. Russia calls the new Ukrainian government illegitimate, and has seized control of Crimea, where it has a major naval base on the Black Sea.
Crimea's parliament has called a March 16 referendum on whether the semi-autonomous region should join Russia outright, a move US President Barack Obama has called a violation of international law. About 60% of Crimea's population identifies itself as Russian.
Russia has also accused the European Union of taking an "extremely unconstructive position" by freezing talks on easing visa barriers and on a comprehensive agreement that would govern ties between Moscow and the EU over Ukraine.
The EU has been pressing for a negotiated solution to the crisis in Ukraine, while Moscow also set out tough conditions which it indicated the West must take to win Russia's co-operation.
The Russian Foreign Ministry said in a statement at an emergency EU summit on Thursday that "Russia will not accept the language of sanctions and threats" and will retaliate if sanctions are imposed. The summit was held in an effort to enforce a call for the withdrawal of Russian forces from the Crimea region and the opening of negotiations between Moscow and Kiev amid severe tension.
It resulted in the suspension of visa talks that began in 2007 and Moscow hopes will eventually enable its citizens to travel to Europe without visas - a major goal for President Vladimir Putin.
The 28-nation EU also agreed to suspend talks on an elusive new pact that would replace a 1997 Russia-EU Partnership and Co-operation Agreement and would involve closer economic co-operation, investment, research, trade and energy relations.
Meanwhile, Mr Putin was in Sochi for the opening of the Paralympics yesterday, where he was shown on television telling the head of the International Paralympic Committee, Philip Craven, he hoped the Games "will lower the heat of passions over Ukraine".
The Ukrainian delegation to the Paralympics said it would participate in the opening ceremony in the Black Sea resort, but warned it could pull out of the 10-day event if Russia makes more military moves.
In comments reported by the R-Sport agency, Valeriy Sushkevich, president of the National Paralympic Committee of Ukraine, said: "I don't remember a situation when the organising country during a Paralympics started an intervention on the territory of a country taking part."
He said if the crisis were to escalate, "we cannot possibly stay here".
In the Crimean capital, Simferopol, 75 people turned out for a rally at the local monument to 19th-century Ukrainian poet Taras Shevchenko. They spoke both Ukrainian and Russian, but waved Ukrainian flags and released white doves into the sky.