Washington - US Secretary of State John Kerry squarely blamed Russian forces on Tuesday for separatist unrest in eastern Ukraine, saying Moscow could be trying to lay the groundwork for military action like it took in Crimea.
"Russia's clear and unmistakable involvement in destabilising and engaging in separatist activities in the east of Ukraine is more than deeply disturbing," Kerry told lawmakers.
"No one should be fooled... by what could potentially be a contrived pretext for military intervention just as we saw in Crimea."
"It is clear that Russian special forces and agents have been the catalyst behind the chaos of the last 24 hours," Kerry added, referring to pro-Russian separatists that seized control of public buildings in three cities in eastern Ukraine.
Ukrainian police cleared pro-Moscow protesters from a regional administration building in Kharkiv in a lightning nighttime operation, but others held out in two more eastern cities, Luhansk and Donetsk.
The protesters have demanded that referendums be held on whether to join Russia like the one that preceded Moscow's annexation of Crimea in March.
Kerry also repeated that the United States, which has imposed two rounds of sanctions on those it believes to be behind the unrest, and its partners were "willing to put into effect tough new sanctions on those orchestrating this action and on key sectors of the Russian economy in energy, banking, mining".
"They are all on the table," he said.