Russia kicks against U.S plans to send the F-22 to Europe as part of its commitment to its Allias.

The U.S. Air Force could be sending some of its most advanced warplanes to Europe in a show of force against Russian actions in Ukraine and elsewhere around the continent, the service's top civilian said Monday.

"The biggest threat on my mind is what's happening with Russia and the activities of Russia," Secretary of the Air Force Deborah James said during a visit to the Paris Air Show. "It's extremely worrisome on what's going on in the Ukraine."

James' remarks were reported by Military.com, Breaking Defense and other websites.

For months, the Pentagon has been rotating aircraft through Europe for exercises with allies under Operation Atlantic Resolve, which it calls "America's commitment to European security."

Participating in those exercises and rotations have been B-2 and B-52 bombers, F-15Cs and A-10 attack planes as well as Army and Navy assets.

James said the F-22 Raptor, the Pentagon's premier fighter, could join that list.

"I could easily see the day -- though I couldn't tell you the day exactly -- when the F-22, for example, rotates in is a possibility. I don't see why that couldn't happen in the future," James said, according to Military.com.

The stealthy F-22s, which became operational in 2005 but only saw their first combat in attacks on ISIS positions in Syria late last year, can be configured to attack other aircraft or bomb ground targets.

"The F-22 cannot be matched by any known or projected fighter aircraft," says the Air Force's fact sheet for the Raptor, which costs about $143 million each. That would include what Russia currently puts in the air. Russian reaction to James' remarks came through state-sponsored media Sputnik International.

One posting on the Sputnik website called any threat from Russia "fictional." Another said Moscow would make moves of its own if the F-22s were deployed.

"Their deployment will certainly be an additional impetus for Moscow to speed up the process of developing and putting on service the Russian response, the fifth-generation T-50 fighter," Sputnik quoted Vladimir Batyuk, from the Institute for U.S. and Canadian Studies of the Russian Academy of Sciences, as saying.

U.S. and Russian forces have had several close calls around Europe since Russian forces took Crimea from the Ukraine in 2014 and supported rebels in other areas of the former Soviet bloc state.

Late last month, a Russian fighter jet, flying at high speed, came within 10 feet of a U.S. Air Force reconnaissance aircraft in international airspace over the Black Sea, U.S Official said

That close call came weeks after another incident between the U.S. and Russia over the skies of Europe, when a U.S. RC-135U flying a routine route in international airspace was intercepted by a Russian Su-27 Flanker in what authorities called an "unsafe and unprofessional manner."

And earlier this month, the U.S. Navy took the unusual step of releasing video of Russian Su-24 aircraft flying past the right side of the guided missile destroyer USS Ross in the Black Sea.

The Cold War has started

Russian military aircraft were dispatched to head off a US warship that was acting "aggressively" in the Black Sea, Russia's state news agency RIA reported, but the Pentagon denied any unusual behaviour.

RIA quoted an anonymous source in Russia's armed forces in Crimea as saying on Sunday that the guided missile destroyer USS Ross was moving along the edge of Russia's territorial waters and heading in their direction.

"The crew of the ship acted provocatively and aggressively, which concerned the operators of monitoring stations and ships of the Black Sea Fleet," RIA quoted the source as saying.

"Su-24 attack aircraft demonstrated to the American crew readiness to harshly prevent a violation of the frontier and to defend the interests of the country."

Pentagon spokeswoman Eileen Lainez said the USS Ross was "well within international waters at all times, performing routine operations".

"The US navy operates routinely in the Black Sea, in accordance with international law," Lainez said, noting the Ross' deployment to the Black Sea had been publicly announced.

Russia's defence ministry was not immediately available to comment on the report.

The incident is the latest example of encounters between Russian and Western militaries, as tensions continue over the crisis in Ukraine and Russia's annexation of the Crimea peninsula, home to Russia's Black Sea Fleet, last year.

Earlier this month, both Britain and Sweden said that they had scrambled fighters to intercept Russian bombers near their territory.

The US said last month that it was filing a complaint to Russia over a Russian fighter's "sloppy" and unsafe interception of a US reconnaissance plane in international airspace over the Baltic Sea.