Washington (CNN) President Donald Trump capped off his dramatic appearance at the annual NATO summit in Brussels, Belgium, on Thursday by teasing another controversial possibility, saying he would not rule out ceasing NATO military exercises in the Baltic States if Russian leader Vladimir Putin requested it during their upcoming meeting in Helsinki, Finland.

Asked if he would cancel them, Trump said, "Perhaps we'll talk about that," referring to Putin, a response that has only fueled the the growing uncertainty over the state of the alliance.

Despite Trump's barrage of acidic rhetoric during the summit, diplomats said the President never explicitly threatened to leave NATO and it remains unclear whether he has the power to do so without Senate approval.

However, Trump's comments about possibly canceling NATO military exercises at Putin's request have amplified fears among European leaders that the President could undermine the alliance by making major unilateral concessions to the Russian President -- who he again referred to as a "competitor" rather than an adversary on Thursday.

One defense official told CNN Thursday that the Pentagon is not anticipating Trump suspending exercises in Eastern Europe.

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