Activist and author David Swanson told Radio Sputnik: “The war rehearsal, or war games, are just insane.”
Mr Swanson, who called the drills “madness”, argued it was no longer clear what NATO’s true purpose was and that its exercises “are great for selling weapons”.
He added: “They are great for building up hostility and maintaining enemies that help sell weapons, but they risk major war.
“And they risk nuclear war.”
Mr Swanson said a petition at RootsAction.org has obtained at least 10,000 signatures calling for an end to the military exercises.
He said: “The US, NATO and other countries that have joined in — Sweden, Finland, et cetera — it’s madness.
“NATO is also planning to celebrate its 70th anniversary on April 4 in Washington, DC — a day that ought to be dedicated to Martin Luther King, Jr.
“Another group I work for, World Beyond War, is working on plans to protest that and celebrate nonviolence and peace rather than NATO’s birthday.
“The other message being sent by all this hostility toward Russia, according to National Security Adviser John Bolton over in Russia tearing up another treaty, was, ‘Don’t mess with US elections’.
“Russiagate liberals have won.”
The NATO exercises seem to be aimed at Moscow, but a retired US general also predicted on Wednesday the US will probably be at war with China within 15 years.
Some 50,000 soldiers, 250 aircraft, 65 ships and 10,000 tanks and other ground vehicles are taking part in the Trident Juncture war games that began Thursday at locations from Iceland to Finland.
The events are intended to test NATO’s response to an attack on Norway – where most of the drills are taking place.
A total of 31 countries are involved in the military drills.
Footage showed treaded vehicles barrelling down muddy forest tracks, soldiers marching through barren northern landscapes and F-18 Super Hornet fighter jets taking off from remote runways.
Independent military analyst Alexander Golts compared Trident Juncture to 1980s NATO drills during the Cold War era.
Mr Golts argued the drills spelt the beginning of a new and reinvigorated Cold War.
He told the Daily Telegraph: “They’re the biggest NATO exercises since the end of the first Cold War and the fact that they are being held just shows that a new Cold War has started.
“This means the confrontation is becoming harsher.”