In the near term, the U.S. administration should work with its European allies to fully implement its decision on visa bans, economic sanctions and to boycott the G8 summit in Sochi. It should also go beyond providing economic assistance to Ukraine and start to think of innovative ways to advance the country’s conventional and non-conventional military capabilities. Russian troops don’t seem to be retreating and it would be foolish not to prepare for an eventuality of not only shots being fired, but perhaps even more dangerous incursions into the country’s cyber and energy infrastructure.

In the long term, it is in the U.S. national security interest to protect Europe’s territory from any future territorial intrusion and other non-military means of political and economic intimidation. The United States should continue applying further reassurance measures for its allies in Central and Eastern Europe, including lifting the embargo on liquefied natural gas exports to decrease the dependency of Europe on Russian gas and providing assurances that the announced U.S. defense budget cuts won’t compromise the U.S. commitment to European missile defense.

Similarly, Obama should fully recommit to NATO and use his two upcoming trips to Europe to outline a clear vision for continued American engagement in NATO after the drawdown from Afghanistan, which should include training, exercises and a serious reevaluation of the current capabilities initiatives to increase their efficacy and applicability to both current and future needs. The United States should also come forward to openly support NATO’s continuing enlargement, starting with Montenegro at the 2014 Wales summit. A Membership Action Plan for Georgia, a country itself attacked by Russia in 2008, should be a priority.

Ukraine is aspiring to join the Western community of values and ideals the same way the countries of Central and Eastern Europe did when they saw their own chance to rebuild their societies 25 years ago. The crisis in Ukraine is a defining moment of Obama’s tenure. It’s time for him to recognize this historic opportunity and get behind the greatest U.S. foreign policy legacy of completing Europe whole, free and at peace. If done right, Obama has a chance to become a president who completed Europe. And the United States will be better for it.

Simona Kordosova is an associate director in the Brent Scowcroft Center on International Security at the Atlantic Council.

Image: President Barack Obama, September 28, 2012 (photo: White House)