US Defense Secretary Lloyd Austin said on Friday that Russia was expanding and modernizing its nuclear arsenal as Russian President Vladimir Putin repeatedly said he could use nuclear weapons to defend Russia, Reuters reported.

“Russia is also modernizing and expanding its nuclear arsenal,” Austin said.

“And while the Kremlin continues its brutal and unprovoked war against Ukraine, the entire world has watched as Putin engages in highly irresponsible nuclear threats,” Austin added.

Russian President Vladimir Putin on Friday vowed to wipe off the face of the earth any country that dares to attack Russia with nuclear weapons.

Putin said Russia does not have a pre-emptive nuclear first strike mandate, unlike the United States, but that Russia’s advanced hypersonic weapons ensure Russia can respond with force if it is ever attacked.