"We don't want a new arms race, so we are focused on how can we respond" in a "firm strong predictable, but also measured and defensive, way," Jens Stoltenberg told reporters alongside Canadian Prime Minister Justin Trudeau in Ottawa.

"We don't want a new Cold War," he said.

He made the remarks when asked about the possibility of new NATO sanctions against Russia after former spy Sergei Skripal and his daughter were poisoned in England on March 4.

London and its allies have blamed Moscow for the attack, citing the use of a Soviet-designed nerve agent Novichok, Russia's record of targeting dissidents and its history of aggression in recent years, from Crimea to cyber-attacks.

"We will continue to strive for a more constructive relationship with Russia," Stoltenberg said.