Story highlights At least six close encounters this year between US and Russian ships, planes

Analysts see the risky maneuvers as a strategy to challenge the U.S., intimidate allies

Washington (CNN) The repeated close encounters between Russian and U.S. warships and planes may not be an accident.

That's the view of analysts who are coming to believe that the risky Russian maneuvers -- there have been at least six close calls this year -- are part of Vladimir Putin's strategy aimed at challenging the U.S.'s global position and intimidating its European allies.

"The Russians believe that if they do a show of force, that they achieve results that promote their interests. In this case, it is a certain degree of intimidation," retired Army Gen. Wesley Clark told CNN.

Clark, who was NATO's supreme allied commander until 2000, added that it "shows that they (the Russians) are willing to stand up to the United States."

The Kremlin has been angered lately by NATO's effort to bolster its eastern flank amid increased Russian military activity in the region.

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