US, Oct. 26 -- India-US relations have reached a consequential crossroads. Three decades of cooperation in defense, technology and regional security now face tariff threats, American objections to Russian oil imports and Washington's dealings with Pakistan. New Delhi must prevent these disputes from eroding a partnership serving both countries' interests.

US Secretary of State Marco Rubio's October 20-21 visit, his second trip to India in five months, offered an opening to arrest the deterioration. Movement in trade talks and easing of certain punitive measures created room for diplomacy. Can Washington turn conciliatory signals into a dependable relationship, or will India face uncertainty whenever American priorities change?

Rubio's ...