Russia's President Vladimir Putin approved a draft bill for Crimea's annexation Tuesday morning.
The Black Sea peninsula on Monday voted overwhelmingly to secede from Ukraine and seek to join Russia.
The decree signed by Putin and posted on the official government website Tuesday morning is one step toward formalizing the annexation of Crimea.
French Foreign Minister Laurent Fabius said Tuesday that Russia's participation in meetings of the G8 group of nations has been suspended.
The other seven countries had already said they had halted preparations for the G8 summit, which is set for June in the Russian resort of Sochi.
Fabius said Tuesday that the seven leading countries will unite without Russia.
Within hours of the vote on Monday, the Crimean parliament formally asked that Russia "admit the Republic of Crimea as a new subject with the status of a republic."
Putin will on Tuesday address a special joint session of Russia's State Duma, or parliament.
Russian forces took control of Crimea in late February following the toppling of Ukrainian President Viktor Yanukovich after deadly clashes between riot police and protesters trying to overturn his decision to spurn a trade and cooperation deal with the European Union in favor of cultivating closer ties with Russia.
U.S. President Barack Obama slapped sanctions on 11 Russians and Ukrainians blamed for the seizure, including Yanukovich, and Vladislav Surkov and Sergei Glazyev, two aides to Putin. The European Union also imposed travel bans and asset freezes on 21 Russian and Ukrainian officials.
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