Russian President Vladimir Putin has attacked the United States for what he said was its "almost uncontained" use of force around the world.
America's "very dangerous" approach to global relations was fuelling a nuclear arms race, he told a security summit.
Correspondents say the strident speech may signal a more assertive Russia.
Mr Putin told senior security officials from around the world that nations were "witnessing an almost uncontained hyper use of force in international relations".
"One state, the United States, has overstepped its national borders in every way," the Russian president said.
"This is very dangerous. Nobody feels secure anymore because nobody can hide behind international law," he said, speaking through a translator.
"This is nourishing an arms race with the desire of countries to get nuclear weapons."
Western leaders in the audience, including Mrs Merkel, looked decidedly glum-faced when President Putin had finished, our correspondent adds.