The Russian invasion of Georgia has sent shock waves throughout the West and the former Soviet space - especially Ukraine. Indeed, Ukraine could be the next potential crisis.

Georgia's increasingly pro-Western course, including growing ties to NATO, has been a thorn in Moscow's side. But it did not pose a serious threat to Russian security. Georgia's army is small, ill-equipped and no match for Russia's, as was amply demonstrated this month.

Ukraine's integration into NATO, by contrast, would have far-reaching strategic consequences, ending any residual Russian hopes of forming a "Slavic Union" composed of Russia, Belarus and Ukraine - a dream that still beats in the breast of many Russians. It would also have important implications for the Russian defense industry, notably air defense and missile production.

In short, the real source of Moscow's anxiety and strategic angst is Ukraine's future political and security orientation. Georgia has largely been a side show.

Russia has a number of means of pressuring Ukraine short of using military force. One is energy. Ukraine is heavily dependent on Russian energy, particularly gas.

Russia has used the gas issue as a foreign policy instrument. Ukraine currently pays $179 per 1,000 cubic meters for gas from Russia - more than three times what it paid in 2004 - and there have been reports that Moscow is considering a further doubling of the price. Russia's long-term strategy is to try to gain control of Ukraine's pipelines by transferring them to a joint venture, as it has done in Belarus, thus enabling it to control both supply and distribution of gas to Ukraine.

The Black Sea Fleet is another potential source of tension. Under an agreement signed in 1997, Ukraine granted Russia basing rights for the fleet at Sevastopol in Crimea until 2017. Ukraine has been pressing Russia to begin discussions on the fleet's withdrawal. But Russia has dragged its feet, suggesting that Moscow may seek to use the presence of the fleet as a means of pressuring Ukraine.

Crimea itself represents a third potential flash point. Crimea is the only region in Ukraine where ethnic Russians constitute an overwhelming majority of the population (58 per cent). Khrushchev transferred the peninsula to Ukraine in 1954 as a gift to commemorate the 300th anniversary of the unification of Ukraine and Russia. At the time, the gesture was largely symbolic, as Ukraine was part of the Soviet Union and few could envisage an independent Ukraine.

Separatist pressures emerged in Crimea immediately following the collapse of the Soviet Union. They subsided after 1995 largely because the Russian separatists were divided, and Moscow, facing separatist pressures in Chechnya, showed little inclination to support them.

However, separatist pressures, while diminished, continue to exist in Crimea. Given Crimea's historic ties to Russia and its majority ethnic Russian population, many Ukrainian officials fear that Russia could try to foment separatist movements in Crimea as a means of putting pressure on Ukraine to curb its ties to the West.

Moscow's tactics in Abkhazia and South Ossetia provide cause for concern in this regard. Russia encouraged and supported separatist movements in both entities, then used the separatist tensions to justify sending "Russian peacekeepers" into the regions. Moreover, it granted Russian citizenship to Abkhaz and South Ossetian residents, and then justified its recent invasion of Georgia on the grounds that it had an obligation to protect Russian citizens.

Western allies have a strong strategic interest in supporting Ukrainian democracy and Ukraine's Euro-Atlantic integration. But this course must be pursued prudently and with great care.

As the Georgian crisis has underscored, there are limits to the ability to influence developments in a region where Russia has strong strategic interests and a preponderance of military power. Thus Europe and the United States need to be very careful about making security commitments they are unwilling or unable to carry out.

This does not mean that Moscow should be given a veto over Ukraine's security orientation or that Ukraine can never become a member of NATO. The door for Ukraine to join NATO should remain open.

But with Russia in a defiant mood and refusing to fully withdraw its troops from Georgia, now is not the time to accelerate efforts to bring Ukraine into the Alliance. Poking an angry bear is not a wise policy. Ask Mikheil Saakashvili.