The U.S. Air Force is considering deployment of the stealth-capable F-22 Raptor fighter jet, the most advanced in its arsenal, to Eastern Europe to quell the fears of Russian hostility among NATO allies. The possible deployment of the fighter jet, which comes just one day after Russia warned against American-led NATO expansion in Eastern Europe, exemplifies the growing divide between Russia and the West since Moscow annexed Crimea in March 2014 and has involved itself in the Ukraine war.

“I could easily foresee the day … when the F-22 might rotate in,” Deborah James, the U.S. secretary of the Air Force, told reporters Monday at the Paris air show, noting she did not know when they could be sent to Europe, where they never have been based. "We face many threats [throughout the world], but Russia is the biggest threat right now. The hybrid warfare that Russia is conducting in Ukraine is extremely worrisome."

Russian Ministry of Defense spokesman General Yuriy Yakubov said the possibility the F-22 and other military assets may be placed in the region is “the most aggressive step of [the] Pentagon and NATO since the Cold War last century,” adding Russia would be left with no option but to build up its forces on its Western border and redeploy short-range missiles to its Baltic stronghold of Kaliningrad.

"The group of forces along the perimeter of Russia's western border will be reinforced first of all, including new formations of tanks, artillery and aircraft units," he said.

To facilitate the move of its forces to border regions, Russia has withdrawn from the Treaty on Conventional Armed Forces in Europe, meaning it is no longer bound by restrictions on the number of aircraft, tanks and troops that can be placed on its own borders.

While in Paris, James also reiterated the importance the United States' NATO allies commit to spending at least 2 percent of GDP on defense as the world grows more unstable. "We would urge the 2 percent target for NATO allies. Now is not the time for [defense] spending to be going down. This is a serious matter," James said, while also highlighting the U.K.’s recent decision to reduce military spending by 500 million pounds ($780 million), which will likely take the U.K.’s spending below the NATO-set 2 percent, nonbinding threshold.