For President Vladimir Putin, who is trying to pull Ukraine back into the Russian orbit, this is a battle he can't afford to lose. He needs Ukraine to make his customs union with Kazakhstan and Belarus viable and he wants to ensure the country stays out of the clutches of the West. He especially rejects the idea of Ukraine having any kind of association with NATO, such as the membership action plan undertaken by former president Viktor Yushchenko immediately after the 2005 Orange Revolution.
Today's president, Viktor Yanukovych, made normalizing relations with Russia his foreign-policy priority when he came to office in 2010 and ended the NATO relationship, though he continued, for a time, Kiev's efforts to conclude an association agreement with the European Union.
According to many observers, Russia believes that, like Belarus four years ago, once Ukraine ends its associations with the West, it is only a matter of time before the country, facing serious economic problems, finds itself caught in Moscow's web.
Washington's interest in Ukraine is precisely the opposite: It wants to see Ukraine as westernized as possible, with membership in associations such as the European Union and especially in NATO. It believes that will make Eastern Europe more stable and secure.
Since the fall of the Soviet Union in 1991, the United States has provided several billion dollars to promote the development of democracy, economic reform and the elimination of strategic nuclear weapons, seeing these things as contributing to security. But Washington achieved its biggest goals in the first decade, when it successfully negotiated the removal and destruction of all strategic weapons.
While some in Washington would like to help Ukraine's protesters win this battle if only to stick it to Mr. Putin, it's not at all clear it would be in the United States' long-term interests, nor is there much stomach these days for aiding what could turn into a civil war.
Europe's interest in Ukraine is primarily economic. It sees the country as a rich market with considerable industrial potential once it is properly supported and managed.
However, the European Union will insist that Ukraine abide by high standards of democracy, human rights and economic transparency. That means the release of former prime minister Yulia Tymoshenko, for starters, who has been imprisoned for seemingly political purposes.
At this point, Ukraine has already slid so far back in its standards of democracy and human rights that, even if Kiev and Brussels signed an association agreement, it would not likely be accepted by all 28 EU members.
Europe worries, too, that even Ukraine's protesters, once seen as peaceful, have now been joined by hard-right militants, and may choose to keep its distance.
Editor's Note: The original print version of this article and an earlier online version incorrectly said the EU has 27 members, not 28. This online version has been corrected.