MIHAIL KOGALNICEANU AIR BASE, Romania (Reuters) - For the squadron of U.S. fighter pilots standing on the runway of an air base in Romania, the mission is clear: show that the United States is ready to flex its military muscles if needed, and don’t provoke the Russians.

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Two advanced F-22 U.S. fighters flew to the base on the Black Sea on Monday for the first time since Washington beefed up military support for NATO’s eastern European allies, who say they are under pressure from an increasingly aggressive Russia.

The men behind the exercise, taking smartphone pictures of their planes and handing out badges and uniform patches to local Romanian crews, know their job is not to lock horns with President Vladimir Putin’s pilots, but to keep their NATO friends happy.

“We’re not here to provoke anybody, we’re here to work with our allies,” says Dan Barina, a 26-year-old pilot on his first trip to a region where tensions have risen markedly since Russia annexed the Crimean Peninsula from Romania’s neighbor Ukraine two years ago.

But they also know that the risks of operating in the region are real.

This month, two Russian warplanes flew simulated close-quarters attack passes near a U.S. guided missile destroyer in the Baltic Sea.

“I guess you can watch the video and see for yourself how those intercepts are,” said Dan Naim, another F-22 pilot, smiling wryly as he chewed cinnamon-flavored gum on board a refueling plane accompanying the fighters.

“If you want to intercept people over international waters, we just want to encourage them to do that in a safe way.”

Knowing that their opponents may want to engage in a high-stakes mid-air staring contest with the West, how would the pilots handle an airborne encounter with a Russian jet?

“The type of missions we run generally are offensive-defensive types of mission. You’re looking to be cool, calm and collected,” said Rob Morgan, a short time after stepping out of the cockpit of his F-22 at the Romanian base.

“Our actions definitely do have greater consequences. We’re very, very careful with what we do. The mission planning that went into something like this was extensive.”

But, laughing, joking and poking around the overgrown cold-war-era Russian-made MiG-29 jets on display at the base, the pilots wear the responsibility of flying the frontier between Putin’s Russia and the West lightly.

“Until you’re in that situation, I don’t know if you really do know what it feels like,” said Barina - nicknamed ‘Scream’ because he reminds some of the figure in Edvard Munch’s expressionist painting.

“If it’s got to be done, it’s got to be done. I’m not sure I’d think about a whole lot else ... It’s the job we all signed up for.”