Crimea appears to be on the fast track for joining up with Russia after Sunday's referendum vote in favor of union with Moscow.
Ukraine and the West are adamantly opposed to the Russian annexation of Crimea, but what are they prepared to do about it? Here's a look at the major players and the choices they face in the Crimea crisis.
Ukraine: Ukraine insists that Crimea remains part of the country and is preparing its armed forces. Defense Minister Igor Tenyukh said the country's military forces were mobilized and ready to fight.
One key question centers on the Ukrainian forces that remain at their bases in Crimea. If Ukraine keeps them there and there's every indication that it will then a long-term standoff could ensue between the Ukrainian and Russian forces in the peninsula.
Ukraine is also looking for Western military help. The White House said it was reviewing the request, but emphasized that the focus was on diplomacy. NATO has so far shown no sign that it is prepared to escalate the crisis militarily with moves such as a no-fly zone over Crimea or placing naval ships in the Black Sea to confront Russian forces.
On the economic front, Ukraine controls the water and electricity supplies to Crimea, but Ukraine's leaders have said they are not planning to cut those off. If Ukraine did, Russia could respond in kind by turning off natural gas to Ukraine.
As Ukraine deals with the Crimea crisis, it's also gearing up for a national election on May 25. This ballot was initially set for next year, but has been moved up following the mass protests that ousted President Viktor Yanukovych in February. Many Ukrainians say they fear that Russia will try to undermine the vote.
Russia: With Crimeans voting Sunday in favor of joining Russia, Moscow now has to decide whether it wants the territory to become a full-fledged part of Russia.
The chairman of Russia's Duma, Sergei Naryshkin, said parliament would act "swiftly and responsibly" and saw no problem with admitting Crimea, the Interfax news agency reported.
Russian President Vladimir Putin on Monday recognized Crimea as a sovereign state, a move seen as a precursor for union between Crimea and Russia.
Russian annexation would bring more criticism and presumably more sanctions. But the punitive measures have been mild so far and Russia seems to be betting that it can weather the consequences. It also argues that sanctions will backfire.
"It's a counterproductive measure," Russian Foreign Minister Sergei Lavrov said recently. "If such sanctions or decisions of this kind are taken, it would not contribute to mutual interests of the businesses, mutual interests of our partnership being developed."
Then there's the question of whether Russia will seek to move on eastern Ukraine, which like Crimea, has a large population of ethnic Russians.
Russia has been carrying out military exercises just across the border from eastern Ukraine. The Russian media and politicians claim that ethnic Russians in this region are at risk and need protection, the same rhetoric that preceded Russia's moves into Crimea.
United States: The U.S. approach has been to impose limited sanctions that target individual Russian political figures considered to be Putin's "Kremlin cronies."
"We'll continue to make clear to Russia that further provocations will achieve nothing except to further isolate Russia and diminish its place in the world," President Obama said Monday at the White House.
Sen. John McCain, the Republican from Arizona, is among the critics describing the U.S. response as tepid.
If the U.S. presses for broader sanctions, American businesses that operate in Russia will almost certainly face a backlash and the U.S. probably will not find solidarity for tougher measures in Europe or elsewhere.
The U.S. is looking for ways to isolate Russia diplomatically, but it's far from clear how much diplomatic pressure Washington can build and sustain. Vice President Joe Biden will try when he travels to Eastern Europe to meet with U.S. allies in Poland and the Baltic states.
In the longer term, there's talk about the U.S. exporting its abundant natural gas to Europe in order to lessen the continent's dependence on Russian supplies. But that would take time.
European Union: EU foreign ministers met in Brussels on Monday and agreed to narrowly targeted sanctions against 21 prominent figures in Ukraine and Russia.
"The hope is by targeting individuals, elites around Putin, you can bring about a push towards a more negotiated solution to the crisis. But I am doubtful that this will have this immediate effect," Gwendolyn Sasse, a political scientist at Oxford University, tells All Things Considered.
Western Europe has many more commercial ties to Russia than the U.S. does, and there's little or no European appetite for a broad-based sanctions campaign.
European leaders have raised the possibility of sending monitors to Ukraine, and eastern Ukraine in particular, in hopes of preventing an escalation there. But as with the other moves, this one is seen as mostly symbolic.
Looking farther down the road, Europe may look for ways to develop its own energy supplies. In several European states, there's been strong opposition to hydraulic fracturing, or fracking, mostly on environmental grounds. The debate may now shift to factor in the question of European dependence on Russian energy.
Greg Myre is the international editor for NPR.org. Follow him @gregmyre1.