The North Dakota-based aircraft, support equipment, and personnel touched down at a Royal Air Force base 150 kilometers (90 miles) west of London, in Fairford, England, the command of US Air Forces in Europe said in a statement.

It did not specify how many US aircraft would be participating in the exercises.

The statement explained that the "long-planned" Bomber Task Force mission aims to improve "cooperation and operational capacity, capability and interoperability" among allies.

"Bomber rotations reinforce the US commitment to NATO allies and coalition partners to maintain our collective safety and sovereignty," it added.

The deployment comes amid fears that Russia is planning to invade its pro-Western neighbor Ukraine, with ten of thousands of Russian troops mobilized along the border.

The US Navy meanwhile said Thursday that four of its destroyers had deployed last month to take part in exercises in the zone covered by the Sixth Fleet, which includes the Mediterranean.

Russia also said Thursday that four of its warships had arrived off the Crimean peninsula for upcoming exercises in the Black Sea, off the southern coast of Ukraine.