NICE, France  President Dmitri A. Medvedev of Russia retreated Friday from his threat to deploy missiles on Europe’s borders, but only if President-elect Barack Obama joined Russia and France in calling for a conference on European security by next summer.

At a meeting in Nice hosted by President Nicolas Sarkozy of France, Mr. Medvedev backed away from the bellicose speech he gave last week, just hours after Mr. Obama won the United States presidential election. On Friday, the Russian leader argued instead that all countries “should refrain from unilateral steps” before discussions on European security next summer.

Mr. Sarkozy, who presided over the meeting between Russia and the 27 European Union nations in his capacity as the union’s president, helped ease the way for Mr. Medvedev’s retreat. The French leader supported the idea of talks on a new security architecture for Europe and suggested that they could be held by the Organization for Security and Cooperation in Europe in June or July.

Both Russia and the United States belong to the organization.

Mr. Sarkozy made clear that he wants the United States to think again about the missile defense systems that it plans to build in Poland and the Czech Republic. Mr. Medvedev last week threatened to respond by stationing missiles in Kaliningrad, a Russian enclave bordering Poland and Lithuania, both of which are members of NATO and the European Union.