U.S. sends F-22 fighters to reassure NATO allies facing Russia, reported reuters.com.

Two highly advanced U.S. fighters flew to the Black Sea on Monday for the first time since Washington beefed up military support for NATO’s eastern European allies who say they face aggression from Russia.

President Barack Obama promised in 2014 to bolster the defenses of NATO’s eastern members, unnerved by Russia’s annexation of Ukraine’s Crimea and the Kremlin’s backing for pro-Russian forces in eastern Ukraine.

A U.S. KC-135 refueling plane flew with the two F-22 Raptor fighters from Britain to Romania’s Mihail Kogalniceanu air base on the Black Sea.

“We’re here today to demonstrate our capability to take the F-22 anywhere needed in NATO or across Europe,” said Squadron commander Daniel Lehoski.

“We want to … actually fly the aircraft and train with our NATO allies,” he told a traveling Reuters reporter.

The F-22s are are almost impossible to detect on radar and so advanced that the U.S. Congress has banned Lockheed Martin from selling them abroad. The U.S. has deployed 12 of them at a British base in eastern England.

“The increased size of the 2016 deployment … allows U.S. Forces to assert their presence more widely across the eastern frontier,” said U.S. Air Force spokeswoman Major Sheryll Klinkel.

“We want to be able to operate out of multiple locations. We want to be able to keep our adversary guessing on where we’re going to go next.”

The West is seeking to strengthen the defenses of its eastern flank and reassure eastern European NATO members – such as Poland, the Baltic states and Czech republic which spent decades under Soviet dominance – without provoking the Kremlin by stationing large forces permanently.

But tensions are rising and Russia says the NATO build-up is stoking a dangerous situation.