WASHINGTON While President Donald Trump is focused on North Korea s nuclear madman, a more alarming threat is rising in South Asia: an explosive mix of nuclear weapons, terrorism and hair-trigger war plans.

Pakistan, already a major nuclear weapons power with well over 100 warheads and the missiles to carry them, is racing to expand its arsenal of short-range tactical weapons meant as a deterrent against India, its larger, more powerful neighbor and blood enemy. India is thought to have around 100 nuclear warheads of its own. (North Korea is estimated to possess enough fissile material to make several warheads.)

But its not the numbers of weapons between India and Pakistan that most worry analysts and diplomats. Its the instability of their nuclear stand-off and the possibility that an accident, a miscalculation or a terrorist attack could ignite a catastrophic nuclear war.

Bitter and distrustful, the two countries have fought four wars since 1947 and skirmished in numerous border clashes that continue to this day . Analysts now warn of a growing risk that another border clash could swiftly escalate into a nuclear crisis.

Just as likely, they say, a terrorist group such as the Pakistan-based Lashkar-e-Taiba could launch an assault inside India, as it did in the Mumbai attacks of 2008 . That might prompt the powerful Indian army to respond by driving deep into Pakistan, an assault that the latter nation could halt only by using its nuclear weapons. India considered such an attack after 174 people were killed in Mumbai eight years ago. In that instance, U.S. officials reportedly were able to talk the Indian military out of such reprisals.