( CNN ) -- Russia 's seizure of Crimea last month may have unfolded with a lightning quickness , but Vladimir Putin and the West are now engaged in a much slower match of wits on a chessboard stretching across most of eastern Ukraine . Rather than going for checkmate , both sides now seem content to wait for the other to make a mistake . Putin made a strong first move by placing 40,000 troops on the border -- and separatists , who are not officially linked to Russia , on the ground in Ukraine . Now Moscow is waiting for the pro-Western government in Kiev to try to retake the parts of the east it has seemingly lost . In Russia 's eyes , any such move from the capital would legitimize an overwhelming counterattack -- a re-run of the Georgia crisis in 2008 , when President Mikheil Saakashvili lost his nerve , shot first , and prompted a Russian invasion . Putin 's problem is time ; he can not wait forever to strike . Troops can not remain ready for combat for many months at a time . Separatists in eastern Ukraine are lost without outside support , and may become nervous as time drags on without any glimpse of a light at the end of the tunnel . On the other side of the board are U.S. President Barack Obama , German Chancellor Angela Merkel and Ukraine 's fledgling government . The biggest challenge for Obama and his German counterpart is to keep a united Western front . They need to uphold a credible threat of massive economic sanctions that could undercut the Kremlin 's funding if it does n't toe the line . But cracks in Western unity are visible everywhere . Europe may be concerned about Russian aggression in Ukraine , but the continent is dragging its collective feet on taking a more confrontational stance towards Putin . Some nations fear Russian pressure , especially on their energy supply . Many are nervous about the price their own countries will pay as a result of tougher sanctions . And nobody is sure yet whether they 're ready to abandon the idea of Russia as a vital partner . Obama , on the other hand , is much more inclined to put the squeeze on the Kremlin . Washington is used to confrontation with Russia -- and with Putin , specifically -- and America is much less economically-connected with its old Cold War rival . American leaders are n't motivated solely by their concern over eastern Europe and Russia reasserting itself as a more aggressive and expansionist power . The U.S. also wants to assert key norms of international order -- namely territorial integrity and the principle to change borders only with the consent of all parties . Ukraine is also a welcome opportunity to signal to allies and rivals alike that America is not retrenching from its global engagements . The impact of the Ukraine crisis on China and the various territorial conflicts with its neighbors will also loom very large on the minds of policy makers in Washington . But whatever the differences among U.S. and EU leaders , the more they act in concert , the better chance they have to achieve their goal : beating back Moscow 's attempt to undermine Ukraine 's sovereignty and territorial integrity . The West also needs to make sure that Kiev 's interim government does n't lose its nerve . As hard as it is for leaders to watch pro-Russian separatists take over their buildings , any large-scale operation in eastern Ukraine could give Putin the opportunity he may be waiting for : invasion with some kind of dubious pseudo-legal cover . It is difficult to say who is in a better position . Putin is a master tactician . Since his years as a KGB agent in Dresden in the 1980s , he has gained much expertise in finding and exploiting the West 's weak spots . And he seems to have broad support at home for his confrontational brand of politics . Putin 's weakness is his regime 's economic dependency on the West . Without the steady flow of income from the sale of gas and oil , brought under control of the Kremlin , the regime would not be able to buy support at home and to finance costly and risky foreign policy adventures . The West has no appetite to confront Russia . But if Putin 's tanks roll into eastern Ukraine out of the blue , without any pretense of legitimacy , he will turn Western opinion even further against him . This could give Merkel and Obama the necessary backing for tough sanctions . If he is to achieve his main goal , which is to prevent Ukraine from associating closer with the West , Putin will have to move fast . He probably needs to have some kind of Russian presence inside Ukraine ( apart from Crimea ) , as control over separatists in the east alone might not be sufficient or sustainable . A full-scale crackdown by the Ukrainian government on separatists would give Moscow the cover to move some Russian troops as `` peacekeepers '' into eastern Ukraine . Once inside the country , another `` frozen conflict '' could be created which would destabilize the country and prevent Western attempts to help Ukraine to get on its feet . This would keep Putin 's longer-term ambition -- to bring Ukraine into a Moscow-led alliance or federation -- very much alive . If the Kremlin comes to the conclusion that the West would n't respond to such a move with painful sanctions -- ones that would damage Putin 's inner circle and be strong enough to sap major sources of income for the Kremlin -- Putin might choose to move along such lines or in other ways . But if the U.S. and EU demonstrate that they are truly ready to use economic warfare to counter the Russian military machine , the West may yet be able to deter Putin from going much further . Something has to give soon . READ MORE : Ukrainian mayor shot as West prepares sanctions . READ MORE : Five ways the Ukraine crisis could end . The opinions expressed in this commentary are solely those of Ulrich Speck .
Russia and the West locked in match of wits over eastern Ukraine . Russia moved thousands of troops to border and is accused of stirring unrest in east Ukraine . Speck : West must unite to pass severe sanctions on Russian regime . Speck : Ukrainian government attempt to retake buildings could spark Russian invasion .