Moscow "properly notified" Washington of the test following its obligations under the 2011 New START treaty, which placed limits on the two countries' nuclear weapons, said Department of Defense Spokesman John Kirby.

"Testing is routine, and it was not a surprise," Kirby told reporters.

The Pentagon "has not deemed the test to be a threat to the United States or its allies," he told reporters.

"Of course, the department remains focused on Russia's unlawful and unprovoked aggression against Ukraine," Kirby added.

Russian President Vladimir Putin on Wednesday announced the test of the next-generation Sarmat ICBM, saying it will make the Kremlin's enemies "think twice."

"This truly unique weapon will strengthen the combat potential of our armed forces, reliably ensure the security of Russia from external threats and make those who, in the heat of aggressive rhetoric, try to threaten our country, think twice," Putin told the army in televised remarks.

Asked about Putin's comments, a senior US defense official said Wednesday that they were "unhelpful."

"We find that rhetoric to be to be unhelpful, given the current context of things, and certainly it's not the kind of thing that we would expect from a responsible nuclear power, especially in the current environment," the official said.

The US Defense Department said on March 2 that it postponed a test of its own Minuteman III ICBM to avoid escalating tensions over Russia's then-week-old invasion of Ukraine.

At the time, Kirby said the postponement was ordered by Defense Secretary Lloyd Austin "to demonstrate that we are a responsible nuclear power."