Leaving NATO is 'the mother of all batsh*t crazy ideas' -- and Trump may do it: Former ambassador
"He (Putin) said he didn't meddle. I asked him again," US President Donald Trump told reporters on Air Force One as he flew to Hanoi for a state visit (Vietnam News Agency/AFP / STR)

Dan Shapiro, who served as U.S. ambassador to Israel under former President Barack Obama, is warning America's European allies to not dismiss President Donald Trump's stated desire to leave NATO as an empty threat.

Writing on Twitter, Shapiro calls leaving NATO "the mother of all batsh*t crazy ideas" -- but he nonetheless thinks Trump is mad enough to try it.

If Trump actually did leave NATO, Shapiro predicts that it would produce mass chaos throughout the world and would increase the chances of a massive war breaking out in Europe.

"For starters, it'd be open season for Russia in Europe," Shapiro writes. "Putin already feels free to menace non-NATO states (Ukraine and Georgia) and 'reacquire' Belarus. First targets: Baltics and Montenegro."

Shapiro doubts that other NATO members would rush in to defend countries like Latvia and Estonia without American military support, which would in effect mean the total crumbling of the alliance.

"Remove the United States from NATO, and the dominoes could start to tumble," he writes. "A divided, internally conflicted Europe with the United States on the sidelines could lead to catastrophic humanitarian, security, and economic consequences."

Read the whole thread here.