Over the past two and a half years, the Obama Administration has made supporting the pro-West Ukrainian government against Russia a matter of policy in virtually every case, even when it made little sense to do so. The most recent round of rising tensions, however, may be changing that.

Though officially the US insists it has no intelligence on Russia’s report of Ukrainian spies trying to infiltrate the Crimean Peninsula, killing a pair of Russian officers, Vice President Joe Biden today spoke with Ukraine’s president, warning him he must “do his part” in avoiding escalation of tensions with the Russians.

That’s a huge shift in US narrative, as in the past they’ve always embraced whatever Poroshenko said about Russia, including his repeated predictions of an imminent Russian invasion of Eastern Europe. In this case, however, it seems the administration is uncomfortable with the road the Ukrainian government is going down, perhaps because unlike in Eastern Ukraine, where Russia was merely a supporter of the rebellion, Crimea is an official member of the Russian Federation, even if not formally recognized by Ukraine as such.

Meanwhile, Ukraine is facing potential diplomatic fallout with Russia itself over the situation, with Prime Minister Dmitry Medvedev warning Russia might ultimately decide to sever diplomatic ties with Ukraine in protest over the attempted infiltration. Ukraine has denied involvement in the matter, though Russia insists that a captured member of the infiltration team confessed to being a member of Ukraine’s spy agency.