Dire Warning

Intelligence Report Estimates Heavy Casualties

Meanwhile, intelligence sources told ABCNEWS that India was preparing to put conventional warheads on missiles that could also carry nuclear warheads.

If these were launched, Pakistan would not know which kind of warhead was headed its way — a purposely ambiguous signal that U.S. officials fear could lead to a miscalculation and spark a nuclear conflict.

A U.S. intelligence report estimated a full-scale nuclear exchange between the two countries would kill up to 12 million people.

Scholars of the region say what they are seeing and hearing now is no longer just big talk.

Analyst George Perkovich of the Carnegie Endowment for International Peace called the situation a "very hairy business that makes the Cuban missile crisis potentially look like child's play."