BRUSSELS—U.S. officials have told allies they will only provide one battalion to the North Atlantic Treaty Organization’s force in Eastern Europe, part of a bid to get European countries to play a greater role in their own defense, according to U.S. and alliance officials.

Plans had been discussed for the U.S. to provide two battalions—approximately 2,000 soldiers—to the force that NATO is building to deter Russian aggression, alongside a battalion from Germany and Great Britain.

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