The leaders of the G-7 countries issues a stern admonition Wednesday to Russia for its aggression in Ukraine, warning that it would not recognize the outcome of a referendum in Crimea and would take collective action if Russia moved to annex the region.

Russia’s annexation of Crimea would be a violation of the United Nations charter, said the G-7 in a statement, as well as several treaties Russia is party to. Crimea’s referendum would be a “deeply flawed process” held under the intimidating presence of Russian troops, it said.

“In addition to its impact on the unity, sovereignty and territorial integrity of Ukraine, the annexation of Crimea could have grave implications for the legal order that protects the unity and sovereignty of all states,” said the G-7. “Should the Russian Federation take such a step, we will take further action, individually and collectively.”

The G-7 nations, which include Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States, have suspended preparations to meet in Sochi, Russia for a G-8 meeting, as the Kremlin paves a path for Crimea’s annexation.

Russian troops occupied Crimea earlier this month, taking effective control of the peninsula as the local government prepared for a March 16 referendum that would allow Russia to officially annex the region.

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