Russia's cross-border shelling of eastern Ukraine and supply of tanks and other heavy weaponry to separatists even after the downing of a Malaysian airliner represented a "clear escalation" of the conflict, the Pentagon said Friday.
"This has been happening, we believe, for several days," Army Col. Steve Warren, a Pentagon spokesman, said of the reported artillery shelling into eastern Ukraine by Russian batteries just across the border in support of the separatists. "This is a military escalation, there's no question about it," Warren said.
Warren's statements followed on earlier charges by Air Force Gen. Philip Breedlove, NATO's Supreme Commander, that Russian involvement had gone beyond support for the rebels to direct military action.
Last week, Breedlove cited a video that appeared to show Russian batteries firing Grad rockets into Ukraine in an effort to stop advances by Ukrainian forces against the separatists. "I am deeply concerned by this latest video that appears to show Russia engaging in military action against Ukraine," Breedlove said.
The U.S. and NATO allies have charged that an Sa-11 surface-to-air missile system supplied to the separatists by Russian forces was responsible for shooting down Malaysian Airlines Flight MH14 last week, killing all 298 aboard.
At the State Department, Deputy Spokeswoman Marie Harf said a Russian column on Friday delivered more heavy weaponry to the separatists, including tanks and rocket launchers.
"Russia will claim these tanks were taken from Ukrainian forces, but no Ukrainian tank units have been operating in that area" in eastern Ukraine, Harf said. "We are confident that these tanks came from Russia," she said.
Officials in Moscow have denied that Russian forces have shelled across the border and counter-charged that Ukraine's military has fired into Russian territory.
When asked about a possible U.S. response, White House Press Secretary Josh Earnest said that the U.S. would continue to press the international community to isolate Russia and discuss tougher economic sanctions "in the hopes of changing [Russian President] Vladimir Putin's calculus."
Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, said that Russia's cross-border firing suggested a "very aggressive" stance by Putin that harkened back to the Soviet invasion of Poland in 1939 ordered by Josef Stalin.
"You've got a Russian government that has made the conscious decision to use its military force inside of another sovereign nation to achieve its objectives -- first time, I think, probably, since 1939 or so that that's been the case," said at the Aspen Security Forum on Thursday.
Dempsey said he was concerned that "Putin may light a fire he loses control of" in inciting Russian ethnic minorities in Eastern Europe.
"Having lit this fire in an isolated part of Europe, it may not stay in Europe," Dempsey said.
Dempsey said Putin was practicing a strategy of "proximate coercion and subversion" by arming and inciting surrogates in neighboring states, and may ultimately face pushback from within the Russian military.
"I think that the Russian military and its leaders are probably somewhat reluctant participants in this form of warfare," Dempsey said.
-- Richard Sisk can be reached at email@example.com