NATO Secretary General Anders Fogh Rasmussen said the Alliance is suspending cooperation with Russia and is boosting cooperation with Ukraine,

The Alliance stood firm in face of Russian challenges by suspending cooperation with Russia and boosting it with Ukraine and strengthening collective defense, Rasmussen tweeted.

NATO chief said Russia's aggression against Ukraine is a wake-up call, and “it reminds us that our freedom, security and prosperity can’t be taken for granted”.

“NATOsummitUK is a critical summit at a critical time. Today and tomorrow we will forge a stronger #NATO for a more complex, chaotic world,” he said.