U.S. Secretary of State John Kerry said that Russia's plan to buy more intercontinental ballistic missiles was concerning and could herald a return to the international hostility of the "Cold War."
Speaking at a military and arms fair on Tuesday, Russia President Vladimir Putin announced the addition of 40 intercontinental ballistic missiles which, he said, were able to overcome "even the most technically advanced anti-missile defense systems."
Kerry and other Western leaders showed their dismay at Putin's statement, however.
"Nobody should hear that kind of announcement from the leader of a powerful country and not be concerned about what the implications are," Kerry said in a teleconference Tuesday.
"Of course it concerns me, we have the START agreement (the nuclear arms reduction treaty between the U.S. and Russia) and we're trying to move in the opposite direction," he said.
Kerry said that, since the 1990s, there had been "enormous cooperation" in the destruction of nuclear weapons that were in the former territories of the Soviet Union.
"No one wants to see us step backwards, nobody wants to, I think, go back to a kind of Cold War status," he added.
The Cold War marked a prolonged period of tensions between Russia and the West, from around the end of World War II until 1991, when the Soviet Union collapsed. The term "cold" refers to the fact that hostilities ranged from propaganda, threats and espionage, but stopped short of open warfare.