Russia is reportedly working on the combat deployment of its Sarmat ICBM. The update comes amid heightened tensions between Russia and Ukraine over strikes with Western long-range weapons on Russian territory and Vladimir Putin updating the nuclear doctrine.

Experts say the missile is more powerful than the Oreshnik used by Russia to strike Ukraine last week, but has been beset by 'catastrophic' failures

Russia plans to deploy its Sarmat intercontinental ballistic missile, also known as ‘Satan 2’, despite setbacks and failed tests. Capable of striking targets in the U.S. or Europe, the missile is a key part of Russia's nuclear arsenal.

The Pentagon says the Oreshnik is a tweak of Russia’s RS-26 Rubezh missile, an intercontinental ballistic missile (ICBM) that has been tested since 2011.

The Russian president says the strike was in response to Ukraine's "use of American and British long-range weaponry".