"I think that the last thing he wants now is a Cold War," Biden told reporters after his first summit with Vladimir Putin, adding that he during the talks had stressed that "certain critical infrastructure should be off limits to attack -- period -- by cyber or any other means."
"Our message remains clear: We are prepared for dialogue, and we have made proposals, but the key to a better relationship lies clearly with Moscow," German Foreign Minister Heiko Maas told reporters before a video call with his NATO counterparts.
"We are there to prevent conflict and war. But the best way of doing that is to send a clear message to any potential adversary that if one ally is attacked, the whole alliance will be there," Stoltenberg said.
Russia's relations with Washington, which cancelled the deployment of two of its own warships to the Black Sea last week after fierce Russian protests, are at a post-Cold war low.
Moscow expelled 10 US diplomats on Friday in retaliation for the expulsion of the same number of Russian diplomats from the United States over alleged malign activity.