The following editorial appeared in Saturday's Washington Post: During a generally upbeat visit to Moscow this month, President Obama made clear that the United States and Russia still have a major difference over the Kremlin's view that some of the countries that formed the Soviet Union must now live under its autocratic 'sphere of influence.' Obama urged the regime of Vladimir Putin to abandon such '19th century' thinking;but since it shows no sign of doing so, governments such as those of Ukraine and Georgia -- both democratically elected and Western-leaning -- could be excused for worrying that a 'reset' of U.S.-Russian relations might happen at their expense. That's why Vice President Biden performed a valuable service this week by traveling to the capitals of both countries. Biden met the Ukrainian and Georgian presidents as well as their leading political opponents, and he delivered major public addresses in which he reaffirmed U.S. support for the two countries' sovereign choices. 'As we reset the relationship with Russia, we reaffirm our commitment to an independent Ukraine,' he said in Kiev. 'We understand that Georgia wants to join NATO. We fully support that aspiration,' he said in Tbilisi. To his credit, the vice president didn't limit his messages to stroking. In Ukraine he forcefully urged feuding political leaders to overcome their quarrels and address their country's heavy dependence on Russian energy imports. In Georgia Biden publicly prodded President Mikheil Saakashvili to deliver on promised political reforms and met with his opposition. He emphasized that two provinces invaded and occupied by Russia last year could be recovered not by military means but only by building a tolerant and prosperous country. The administration must now determine how best to follow Biden's words with actions. The vice president announced the establishment of a U.S.-Ukrainian working group on energy security, which could help Ukraine achieve the efficiency reforms that would free it from dependence on Russia -- which has twice cut off supplies of gas in midwinter. But in Georgia the U.S. delegation was noncommittal in response to Georgian requests that the United States supply defensive weapons and join a European Union mission that monitors the volatile ceasefire line with Russia. The administration may be right to be cautious about weapons sales, while continuing to train the Georgian army. But, if requested by the European Union, it should join in the monitoring mission. Placing U.S. personnel on the ground would eliminate any doubt about America's stance against Russian neo-imperialism -- and make it less likely that Putin would again attempt to subdue a neighbor by force. 