Michael Kugelman, a Washington-based South Asia analyst and writer for the Foreign Policy magazine, said India is now a much closer U.S. partner than Pakistan.

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.”