Whitaker said last month's attempted drone attack at Germany's Leipzig/Halle Airport, which Berlin has blamed on Russia, was more worrying than other recent incidents NATO members have faced.

Kremlin strongly denies Germany terror attack bid but NATO backs its ally and tension between the alliance and Moscow plunge to a post WW II low and dramatic diplomatic bust-up

"Activating Nato's Article 4 [triggering the mechanism among member states in case of a threat] would have been justified, especially because it is not only Germany that is under…