Mr. Medvedev raised the issue directly with President Obama this month at an Asia-Pacific Economic Cooperation meeting in Hawaii. After those face-to-face talks, Mr. Medvedev said, “Our positions remain far apart.”

Since then, he and other Russian officials have made a steady stream of public statements warning of the consequences of a failure by the two sides to reach some accommodation.

American officials insist that the Europe-based missile-defense system was intended to address a threat from Iran — a position that was reiterated by the White House and the Pentagon after Mr. Medvedev’s televised remarks on Wednesday.

“In multiple channels, we have explained to Russian officials that the missile-defense systems planned for deployment in Europe do not and cannot threaten Russia’s strategic deterrent, said Tommy Vietor, a spokesman for the National Security Council. “Implementation of the New Start Treaty is going well is going well and we see no basis for threats to withdraw from it. “We continue to believe that cooperation with Russia on missile defense can enhance the security of the United States, our allies in Europe, and Russia, and we will continue to work with Russia to define the parameters of possible cooperation.”

Mr. Obama ordered a major redesign of the missile-defense plans he had inherited from his predecessor, George W. Bush, opting to move the system closer to Iran and to build it faster. Mr. Bush had favored placing interceptor missiles in Poland and a radar system in the Czech Republic.

In his remarks, Mr. Medvedev said there was still room for negotiation. But he accused the United States and NATO of being unwilling to consider Russia’s point of view. “They are not going, at least as of today, to take into consideration our concerns about the architecture of the European missile defense system,” he said, “They are saying, ‘This is not against you, don’t worry.’ They are trying to calm us down.”

But in what was clearly a reference to the United States Congress, Mr. Medvedev said there were reasons not to trust the assurances from the Obama administration. “Legislators in some countries openly state,” he said, “ This is against you.’ ”