Vice President Joe Biden on Sunday "expressed concern that separatist leaders have refused to reciprocate" a ceasefire offer Friday from Ukrainian President Petro Poroshenko in a phone call with the Ukrainian leader and noted that "the United States was working closely with its G-7 partners to prepare further economic sanctions against Russia if Moscow did not take actions as described in the G-7 Leaders declaration to stop the flow of arms and militants across the border and use its influence to publicly call on the separatists to lay down their arms."
The same day the statement was released, Ukrainian official claimed 10 Russian tanks with support vehicles had crossed the border — heavy military aid destined for separatist camps.
U.S. officials confirmed Russian activity near the border, adding that more tanks were on the way to Ukraine from bases in southwest Russia. They also stated that Russia has deployed troops to within several kilometers of the Ukrainian frontier.
Since its successful invasion and annexation of Crimea earlier this year, Russia has avoided aggression against Ukraine that would bring unwelcome attention from the West. This is part of a savvy military strategy characterized by "operational ambiguity to create confusion ... and creating points for plausible disengagement," according to Michael Kofman writing in The National Interest.
This approach appears to be working, as it has drawn only a feeble response from the U.S. and its European allies.
On Friday, the U.S. imposed minor sanctions on seven pro-Russian rebel leaders through the Department of the Treasury. The leaders have been "blacklisted," meaning they can no longer access U.S.-based assets -- to the extent they have any -- not likely -- and can no longer deal with U.S. firms.
Additionally, the U.S. is considering "scalpel" sanctions to Russia's financial, defense and high technology sectors to accompany the financial and travel restrictions imposed on 11 prominent Russian and Ukrainian politicians in March.
The initial round of sanctions was criticized as "so weak that it's embarrassing" at home; it was laughed off by the targeted politicians. The State Department's brandished scalpel is likely to meet the same response.