The Russian military on Friday announced massive drills of its strategic forces, a stark reminder of the country's nuclear might amid Western fears that Moscow might be preparing to invade Ukraine.

The Defense Ministry said Russian President Vladimir Putin will personally oversee Saturday's exercise, which will involve multiple practice launches of intercontinental ballistic missiles and cruise missiles.

The ministry said it planned the maneuvers some time ago to check the readiness of Russia's military command and personnel, as well as the reliability of its nuclear and conventional weapons.

The war games follow U.S. President Joe Biden's warning on Thursday that Russia could invade Ukraine within days.

Western fears focus on an estimated 150,000 Russian troops – including about 60% of Russia's overall ground forces – concentrated near Ukraine's borders. The Kremlin insists it has no plans to invade.

But Moscow has demanded that the U.S. and its allies keep Ukraine and other ex-Soviet nations out of NATO, not deploy weapons in Ukraine and pull back NATO forces from Eastern Europe.

Washington and its allies bluntly rejected the Russian demands and Moscow threatened to take unspecified "military-technical measures" if the West continued to stonewall.

Russia holds massive drills of its strategic nuclear forces on an annual basis, but the maneuvers planned for Saturday pointedly involve the Black Sea Fleet. The fleet is based on the Crimean Peninsula, which Russia annexed from Ukraine in 2014.