Asia is facing a nuclear menace that has nothing to do with North Korea. If that appears unlikely, think about the divisions and outright hostilities among three nuclear powers with common borders.

The common denominator is China, which has been playing India and Pakistan, the other two neighboring nuclear states, for years. The immediate problem is Pakistan, which is broiling under the pressures of terrorism, near-bankruptcy, and near-insoluble squabbling among its generals and politicians.

“Southern Asia could be entering an accelerated nuclear arms race,” a senior adviser at the United States Institute of Peace, David Markey, warns. “Uneven waves of new investments in capabilities and delivery systems will alter perceptions of deterrence and stability in dangerously unpredictable ways.” 

Those aren’t the only problems. Pakistan now is a tinderbox, as opposition political forces face off against one another and the government deals with intractable threats from fanatics who may be operating with the backing of the group now in charge in Afghanistan, the Taliban. 

It’s a tragic reflection of the problems besetting Pakistan that a suicide bomber made his way into a mosque at Peshawar, near the Afghan border, and killed 101 people with an explosive device. Incredibly, most of the victims were policemen or members of their families living within a supposedly secure area. Just as disturbing: The police don’t know who was responsible, though the culprits seem to have been affiliated with Pakistan’s wing of the Taliban. 

As the Peshawar attack recedes into the history of terrorism in the region, Pakistani leaders are stymied, and divided, over what to do to turn the country around. Pakistan’s prime minister, Shehbaz Sharif, has said the government faces no alternative but to accept the “impossible demands” of the International Monetary Fund for staving off financial disaster that would inevitably inflame tensions.

Mr. Sharif cannot even persuade the firebrand opposition political leader, Imran Khan, who was ousted as prime minister last April in a “no confidence” vote, to join in an emergency conference next week in which he would hope to gain a consensus on a response to the IMF. Mr. Shariff aims at least to convince political rivals of the IMF program, on which he said “we will have to agree.”

Not if Mr. Khan has any say in the matter. “Pakistan continues to face multiple sources of internal and external conflict,” another study by the U.S. Institute of Peace said. “Extremism and intolerance of diversity and dissent have grown, fueled by a narrow vision of Pakistan’s national identity, and are threatening the country’s prospects for social cohesion and stability.”

With barely more than $3 billion in reserve for imports, Pakistan suffers from what the U.S. Institute of Peace says is “the inability of state institutions to reliably provide peaceful ways to resolve grievances.” The impasse, USIP says, “has encouraged groups to seek violence as an alternative.”

The fractures and fissures in Pakistan, the world’s fifth-largest country, with a population of 231 million, have immediate repercussions in relations with China and India, each of which has about 1.4 billion people.

Perpetually in simmering conflict with India over divided Kashmir, Pakistan also threatens India with more than 160 nuclear warheads, a few more than India’s stockpile. China, which has more than 400 warheads, at odds with India over their long frontiers in the Himalayas, has close relations with Pakistan, through which it’s built a road over 15,000-foot-high mountain passes to the port of Gwadar on the Arabian Sea.

“Southern Asia — India, Pakistan and China — is the only place on earth where three nuclear-armed states have recently engaged in violent confrontations along their contested borders,” Mr. Markey wrote. “The problem of nuclear stability in Southern Asia is getting harder to manage because of geopolitical changes, such as rising India-China border tensions.”

China in recent years has been tightening its ties to Pakistan as a foil against India, Pakistan’s historic enemy ever since the division of the Indian subcontinent in 1947 at the end of British rule. China has drawn Pakistan away from America, which decades ago saw Pakistan as an ally bound together in two regional pacts, the Southeast Asia Treaty Organization and Cento, the Central Treaty Organization, formed by the Baghdad Pact of 1955. Both have long since disbanded.

“The presence and influence of China, as a great power and close ally of Pakistan,” a USIP report said, “has both the potential to ameliorate and exacerbate various internal and external conflicts in the region.”