WASHINGTON, March 02, /ITAR-TASS/. U.S. Secretary of State John Kerry has threatened Russia with “very serious repercussions” for Moscow’s decision to take steps towards defense of the Russian-speaking population in Crimea and other regions of eastern and southern Ukraine.

“Russia is in violation of the sovereignty of Ukraine. Russia is in violation of its international obligations,” he claimed.

He indicated that the U.S. and “other countries” might take the sanctions that would isolate Russia economically in case of Moscow’s decision to introduce troops to the Ukrainian territory for the defense of national interests and the ethnic Russian population there, which the upper house of Russian parliament authorized on Saturday.

Kerry said G8 nations and some other countries were prepared “to go to the hilt to isolate Russia" with a wide array of options available to them, adding that “Russia has major economic challenges."

In the light of it, he made a particular stress on the “the ruble already going down” and also mentioned bans on the issuance of travel visas and freezing of assets.