Politicians in the Russian Duma are now considering a vote that will allow Russian president Vladimir Putin to send combat formations into Ukraine.It also threatens fresh sanctions against Russia, whose economy is crumbling under previous rounds of Western sanctions and a collapse in oil prices.
US Secretary of State John Kerry is set to meet Russian Foreign Minister Sergei Lavrov in Rome on Monday amid the toughening American response.
Russia`s foreign ministry said the new US legislation put a "powerful bomb" under US-Russia bilateral ties.
"The openly confrontational nature of the Ukraine Freedom Support Act approved by both houses of the US Congress without debate and proper voting cannot cause anything but deep regret," said ministry spokesman Alexander Lukashevich.