Despite numerous last-ditch efforts to negotiate with Russia to keep diplomacy regarding Ukraine on life support, it appears time has run out on President Joe Biden.

The White House all but made it official by calling Russia's latest movement into separatist territories "an invasion." 

Stuart Kaufman, professor of international relations and public policy, said the main issue is the idea of Ukraine joining NATO. 

"Putin insists that Ukraine must never join NATO. The American people agree that Ukraine is not worth defending with American lives," Kaufman said. "Before the crisis, the Ukrainian people were also uninterested in joining NATO. NATO should have made a decision to stop expanding altogether – not because of Russian pressure, but because it is not in our interest for it to expand further."

But now, with the artillery shelling begun in the Donbas and Russian troops ordered into the separatist areas, it's too late, Kaufman said.

"The war has already begun. NATO will eventually agree to stop expanding anyway, but it will be too late to save Ukraine from a new war."

Kaufman, the former director for Russian, Ukrainian and Eurasian Affairs for the U.S. National Security Council Staff, said another point that was widely missed was the significance of Russia's recent nuclear weapons exercise. 

"This was an unsubtle reminder to NATO members about Russia's nuclear arsenal. It was a tacit deterrent threat: stay out of Ukraine (militarily), or nuclear weapons use could be considered," he said. "This is just further evidence that NATO membership for Ukraine was never really in the cards. Russia is willing to make such threats; the US would – or at least should – never be."