The U.S. and its allies announced Monday that they would, for now, exclude Russia from the G8 and boycott a planned summit in Sochi in retaliation over its Crimea takeover.
President Obama announced Thursday that he is imposing sanctions on additional senior Russian officials and others over the country's annexation of Crimea.
Russia reportedly is prepared to change its stand on Iran nuclear talks in a high-stakes gamble to counter expanded sanctions by the United States and the European Union over Crimea.
Russian President Putin claims Crimea is now part of Russia. Signs treaty to take over country.
Russian President Vladimir Putin signed a decree on Monday recognizing Ukraine's Crimea region as a sovereign state.
President Barack Obama said Monday that new sanctions on Russian officials will "continue to increase the costs" on its government and that the United States is prepared to impose further sanctions if needed.
After Crimeans voted overwhelmingly to join Russia, many are left wondering what is next.
A joint naval exercise of U.S., Bulgarian and Romanian naval forces in the Black Sea has started, the Bulgarian navy said on Wednesday.
President Obama meets with the new Prime Minister of the Ukraine to talk about the country's future.
President Obama calls for international monitors in Ukraine, says Russia's actions violate international law.
The House has approved a $1 billion loan guarantee package for Ukraine, as part of the U.S. effort to support the new government as Russia continues to occupy the Crimean Peninsula.