WASHINGTON, July 29 – President Barack Obama escalated U.S. economic sanctions against Russia on Tuesday for its aggression against Ukraine but dismissed suggestions the growing chill in U.S.-Russian relations marked the start of a new Cold War, Reuters reported.

The United States and the European Union, in a carefully coordinated action, announced targeted new sanctions against Russian banks, energy and defense firms.

It was the West's most serious response yet to what it calls Russian instigation of and continuing support for the separatist uprising in the east and the shootdown of a Malaysian passenger jet on July 17 over eastern Ukraine.

Obama, speaking at the White House, said the sanctions would have a "greater impact on the Russian economy than we've seen so far" in a drive to force Moscow to stop backing the separatists.

Until now, Europe had stopped short of tougher steps against Russia for fear of retaliation. Obama said the new sanctions were a sign of "the waning patience Europe has with nice words from President (Vladimir) Putin that are not matched by actions."

Senior U.S. officials voiced growing alarm about a Russian troop buildup on the border with eastern Ukraine and a continued supply of heavy weaponry to the separatists.

Still, Obama did not seem inclined to provide lethal military aid to Ukraine, saying the Ukraine military was "better armed than the separatists" and the issue at hand was "how to prevent bloodshed in eastern Ukraine."