Even so, Mr. Medvedev’s timing was notable. He is expected to hold his first meeting with President Obama in early April in London on the sidelines of the summit gathering of the Group of 20, which comprises industrialized and developing countries and the European Union.

He has said recently that he is looking forward to the meeting, and both he and Russia’s paramount leader, Prime Minister Vladimir V. Putin, have expressed measured optimism about improving relations with the United States under the new administration.

The Obama administration played down the significance of Mr. Medvedev’s remarks, with the White House spokesman, Robert Gibbs, saying they were “largely for domestic consumption.” He added that “NATO and the United States have worked and will continue to work with Russia on issues of mutual concern, specifically in areas like terrorism and proliferation.”

Nevertheless, Mr. Medvedev’s comments on Tuesday indicated that the Kremlin did not want the United States and its NATO allies to presume that Russia was coming to the table in London from a position of weakness.

“An analysis of the military and political situation in the world shows that there are a range of regions where there remains serious potential for conflicts,” Mr. Medvedev said. “Threats remain that can bring about local crises and international terrorism. NATO is not halting its efforts to widen its military infrastructure near the borders of our country. All of this demands a quality modernization of our armed forces.”