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Former U.S. Ambassador to Russia Michael McFaul has advised Americans doubting the illegitimacy of the Russian annexation of Crimea and aggression against Ukraine to project a similar situation onto America.

"When Americans tell Ukrainians to be more pragmatic when dealing with Russia, I wonder how pragmatic we Americans would be if China annexed Hawaii, Canada invaded Maine, or Mexico supported separatists in California?" he wrote on Twitter on February 8.

The posting sparked a lively discussion, including provocative statements by users with Russian profile names.

Read alsoUkraine says Russia attacks its border guards in Luhansk region across the borderDuring Barack Obama’s first presidential term, McFaul worked as special assistant to the U.S. president on national security. From 2011 to 2014 he headed the United States Embassy in Moscow.

Since his dismissal from the diplomatic service, McFaul has been as a leading expert on Russia and American international politics. Now he is a professor of political sciences at the Center for Democracy, Development and the Rule of Law in Stanford.