RIA-Novosti, Alexei Nikolsky, Presidential Press Service/AP
The New York Times' Michael Gordon and Eric Schmitt report, citing Western officials, that Russia has nearly doubled its battalions along the Ukrainian border in recent weeks. There are now 17 more battalions and an additional 19,000 to 21,000 troops that compose a "battle-ready force of infantry, armor, artillery and air
Western officials also told the Times that Russia has upped its number of surface-to-air units from eight to 14, and they have deployed more than 30 artilleries.
Western intelligence officials told the paper it's unclear what Putin is planning, but it's clear they are worried about what would be, for all intents and purposes, an invasion under the guise of a "peacekeeping" operation.
"That's a very real option," a senior Defense Department official told the Times. "And should Putin decide, he could do that with little or no notice. We just don't know what he's thinking."
The moves come as Ukrainian forces find themselves in increasingly good position on the battlefield against pro-Russian separatists, who the West has accused Russia of supporting throughout the Ukrainian crisis. Western officials said Putin may be feeling pressure to intervene to tip the balance toward the separatists, but he could be worried about the uncertain repercussions that would come from such a radical escalation.
A "peacekeeping" operation is also something about which the White House has also worried in recent weeks.
"Ukrainian forces are right now making major gains to regain sovereignty in the east, but at the same time, Russia is doubling down on its own efforts to support the separatists and destabilize the country," deputy national security adviser Tony Blinken said last week. "Indeed, it is cynically using all of the attention focused on the crash of MH17 as a cover and distraction for its own efforts. It's increased the provision of heavy weaponry across the border. We've seen convoys of tanks, multiple rocket launchers, artillery and armored vehicles. There's evidence it's preparing to deliver even more powerful multiple rocket launchers.
"It is firing from positions inside of Russia into Ukraine - something that we documented this weekend. And we've seen a significant re-buildup of Russian forces along the border, potentially positioning Russia for a so-called humanitarian or peacekeeping intervention in Ukraine."
The U.S. and European Union last week leveled a new, more punishing round of sanctions on Russia last week in the wake of Russia's continued build-up of support for the separatists in the wake of the shooting down of Malaysia Airlines Flight 17.
When asked Monday if he thought the sanctions had at all changed Putin's calculus with respect to Ukraine, White House press secretary Josh Earnest said the White House has "not seen the kinds of actions that we would like to see."