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 it’s not the numbers of weapons between India and Pakistan that most worry analysts and diplomats. It’s 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.

Faisal Mahmood/Reuters Pakistan displays its nuclear-capable NASR missile battery during a military parade in Islamabad on March 23, 2017.

In other all-too-possible scenarios, Pakistani extremists could attempt to obtain a nuclear weapon for themselves. Radicalized members of the Pakistani armed forces might provide the terrorists with insider help.

Past terrorist attacks on Pakistani military bases have already been staged with insider help. In 2011, extremists fought their way into the heavily guarded Mehran naval air base, blowing up aircraft and holding off commandos for 16 hours. In 2014, they tried to hijack a Pakistani warship.

Strategists also suggest that Pakistani jihadists might stage a terrorist attack in India with the intention of provoking a crisis between the two countries. When Pakistan began removing its weapons from secure storage to stage them for a possible launch, the terrorists would pounce and steal one or more warheads.

“The whole South Asian subcontinent is becoming more and more of a nuclear powder keg,” said Matthew Bunn, a nuclear weapons analyst at Harvard University’s Belfer Center for Science and International Affairs. “You can easily imagine an inadvertent process of escalation to an all-out nuclear war that neither wanted, provoked by terrorism.”

Scott Sagan, senior political scientist at Stanford University’s Center for International Security and Cooperation, puts the risk of an India-Pakistan nuclear clash at a higher threat level than the current U.S. confrontation with North Korea. Dealing with North Korean leader Kim Jong Un is dicey and uncertain, but with Pakistan, he said, “the U.S. influence is far more limited.”

An all-out nuclear war that set Indian and Pakistani cities burning would produce enough smoke and particulate debris in the upper atmosphere to cause global temperatures and precipitation to plummet. Corn and soybean yields in the U.S. Midwest and elsewhere would be cut by 20 percent and there would be massive global food shortages for years, according to some climate models.

The pressure in the region to escalate to the use of nuclear weapons has been intensified by India’s adoption of “Cold Start,” a military strategy that calls for lightning strikes with tank columns and artillery deep into Pakistani territory at the start of a conflict. The shift in strategy came after Indian forces based in the country’s interior were unable to quickly punish Pakistan after Lashkar-e-Taiba terrorists overran the Indian parliament in late 2001. Subsequently, India moved quick-strike battle groups close to the border with Pakistan, where they remain on alert.

In response, Pakistan has deployed short-range Nasr missiles, which can carry nuclear warheads and hit targets about 35 miles away, into its own border region. There are some reports that the country is developing nuclear artillery shells and land mines as well. If war were to break out, Pakistan would have to use these weapons quickly, before their locations were overrun by Indian troops.

If any optimism is to be found in this war scenario, it is that by aiming its nuclear weapons at Indian troops, rather than civilian population centers, Pakistan would give India “little justification for a disproportionate nuclear strike on Pakistan’s strategic centers,” according to Indian analyst Sajid Farid Shapoo.

Experts are especially worried that terrorists will play on the historic enmity between India and Pakistan to trigger an unintended nuclear exchange.

“The combination of tactical nuclear weapons and Cold Start doctrine provides an opportunity for terrorist elements to initiate a nuclear war,” writes Shahzeb Ali Rathore, an analyst at the International Center for Political Violence and Terrorism Research in Singapore.

Parts of the Pakistani military and intelligence services are closely tied to various militant groups and have sympathizers within them. Matthew Bunn, a nuclear weapons analyst at Harvard

The tricky balance for Pakistan is to secure its nuclear weapons against theft or misuse, but still have them ready for launching in a crisis. Although the security arrangements are highly secret, Pakistan is believed to store its nuclear warheads disassembled and at a distance from the airfields and missile sites where they would be prepared for use.

Bunn recently spoke with officers of Pakistan’s Strategic Plans Division, which is responsible for securing the nation’s nuclear arsenal. He said the risk that terrorists could hijack a warhead is serious.

“We know that various parts of the Pakistani military and intelligence services are closely tied to various militant groups and have sympathizers within them,” Bunn told HuffPost. Members of the military and security forces can be radicalized “in a matter of months,” he said. “Pakistanis say that won’t happen to them. But it strikes me as something to worry about, given the repeated incidents of insider threats at other Pakistani military organizations.”

Last year in Washington, Pakistan officials sought to reassure an international gathering of nuclear security officials that they have strengthened security measures ― including, according to a statement, “deploying radiation detection equipment at several entry and exit points to deter, detect and prevent illicit trafficking of nuclear and radioactive materials.” The Pakistan Embassy in Washington did not respond to requests for comment for this story.

The United States may have secretly provided Pakistan some technical advice on securing nuclear weapons in the past, but that offers only limited comfort. “Whatever assistance we’ve given them, it’s impossible to know how well they’ve implemented it,” said Sagan.

Bottom line: “Pakistan knows it has an internal terrorist problem and a personnel reliability problem as well,” Sagan said. The risk of terrorists obtaining a Pakistani nuclear weapon “is a huge problem, and it’s one that can be mitigated somewhat but it can’t be eliminated.”