Russia's announcement that it is developing a new generation of "invincible" nuclear weapons does not herald the start of a new arms race, the Kremlin has said.
Russia also denied a US accusation that it was breaching arms control treaties agreed during the Cold War.
On Thursday, President Vladimir Putin unveiled what he said was a new arsenal of advanced weaponry including nuclear devices immune to enemy interception.
Illustrated by computerised animations, including one that appeared to show an attack on Florida, Mr Putin used his state-of-the-nation speech to warn that Moscow would regard a nuclear attack on its allies as an attack on Russia itself and would respond swiftly.
"We would consider any use of nuclear weapons against Russia or its allies to be a nuclear attack on our country. The response would be immediate," he told the audience of Russian politicians and senior officials.
Mr Putin said the weapons made NATO's US-led missile defence system "useless" and signalled the end to Western efforts to check Russia's nuclear ambitions.
"I want to tell all those who have fuelled the arms race over the last 15 years, sought to win unilateral advantages over Russia, introduced unlawful sanctions aimed to contain our country's development: all what you wanted to impede with your policies have already happened," Mr Putin said.
"You have failed to contain Russia."
He said the development of the new weapons was in response to the US withdrawing from a Cold War-era treaty that banned missile defences and Washington's moves to develop a missile defence system.
The US State Department expressed outrage, but at the same time was scathing of what it called Mr Putin's "cheesy" animations.
Spokeswoman Heather Nauert said: "It was certainly unfortunate to have watched the video animation that depicted a nuclear attack on the United States.
"That's something that we certainly didn't enjoy watching. We don't regard that as the behaviour of a responsible international player.
"President Putin has confirmed what the United States government has known for a long time but that Russia has denied prior to this.
"Russia has been developing destabilising weapons systems for more than a decade in direct violation of its treaty obligations."
Two of the weapons revealed by Mr Putin were a nuclear-powered cruise missile and an artificial drone.
He said the missile, which was tested late last year, has an unlimited range and can penetrate any missile defence.
The drone can carry a nuclear warhead and target both aircraft carriers and coastal facilities, the Russian leader also claimed.
He added that the names for the two weapons had not yet been chosen and suggested the country's defence ministry could run a nationwide contest to pick the names.
A new heavy intercontinental ballistic missile (ICBM) called Sarmat is also under testing and has a range and number of warheads exceeding the capabilities of its predecessor, Mr Putin added.
Another new weapon mentioned in the speech was Avangard, which Mr Putin described as an intercontinental hypersonic missile that would fly towards targets at 20 times the speed of sound and strike "like a meteorite, like a fireball".
In comments quoted by the state-run Sputnik website, a Kremlin spokesperson said: "The president noted that the development of the weapons was nothing but Russia response to the US withdrawal from the [Intermediate-Range Nuclear Forces Treaty] treaty and the creation of the global air defense system that infringes upon the nuclear balance and is capable of neutralizing Russian strategic forces," Peskov said.
He added that the weapons were "the way to maintain the nuclear balance as it is necessary for the international peace and stability".