Most likely it would be a joint US/Indian operation, and there are definitely contingency plans for such an eventuality. A combination of airstrikes and US SpecOps raids will do it, but India will not go into Pakistan proper with ground troops. They were prostrate at Indira's feet in '71 IOTL but apart from superpower pressure from both sides, she didn't want an insurgency that would make Vietnam, Iraq and Afghanistan combined look like child's play.