NEW DELHI — A deadly attack on tourists in Indian-controlled Kashmir has again moved India and Pakistan closer to war as the two rivals downgraded diplomatic and trade ties, closed the main border crossing and revoked visas for each other’s nationals.

The Pakistani government said that if India followed through on a threat to block rivers it would take it as “an act of war.”

The U.S. State Department said on Sunday Washington was in touch with both India and Pakistan while urging them to work towards what it called a "responsible solution" as tensions have risen between the two Asian nations following a recent Islamist militant attack in Kashmir.