American and British diplomats fear Pakistan's nuclear weapons programme could lead to fissile material falling into the hands of terrorists or a devastating nuclear exchange with India.

The latest cache of US embassy cables released by WikiLeaks contains warnings that Pakistan is rapidly building its nuclear stockpile despite the country's growing instability and “pending economic catastrophe”.

Mariot Leslie, a senior British Foreign Office official, told US diplomats in September 2009: “The UK has deep concerns about the safety and security of Pakistan's nuclear weapons,” according to one cable classified “secret/noforn [no foreign nationals]”.

Seven months earlier the US ambassador to Islamabad, Anne Patterson, cabled to Washington: “Our major concern is not having an Islamic militant steal an entire weapon but rather the chance someone working in government of Pakistan facilities could gradually smuggle enough material out to eventually make a weapon.”

The leak of classified US diplomatic correspondence exposes in detail the deep tensions between Washington and Islamabad over a broad range of issues, including counter-terrorism, Afghanistan and finance, as well as the nuclear question. The cables also revealed that:

- Small teams of US special forces have been operating secretly inside Pakistan's tribal areas, with Pakistani government approval, while senior ministers have privately supported US drone attacks.

— The ambassador starkly informed Washington that “no amount of money” from the US would stop the Pakistani army backing Islamist militants and the Afghan Taliban insurgency.

— The US concluded Pakistani troops were responsible for a spate of extrajudicial killings in the Swat Valley and tribal belt but decided not to comment publicly to allow the army to take action on its own.

— Diplomats in Islamabad were asked by the Pentagon to survey refugee camps on the Afghan border, possibly for air strike targeting information. - The president, Asif Ali Zardari - whose wife, Benazir Bhutto was assassinated - has made extensive preparations in case he too is killed, and once told the US vice-president, Joe Biden, that he feared the military “might take me out”.

Pakistan's rulers are so sensitive about their much-prized nuclear weapons that in July 2009 they stalled on a previously agreed plan for the US to recover and dispose of highly enriched uranium spent fuel from a nuclear research reactor, in the interests of preventing proliferation and theft. They told the US embassy: “If the local media got word of the fuel removal, “they certainly would portray it as the US taking Pakistan's nuclear weapons”.

US fears over Pakistan were spelled out in an intelligence briefing in 2008. “Despite pending economic catastrophe, Pakistan is producing nuclear weapons at a faster rate than any other country in the world,” the secret cable said.

Leslie, director general of defence and intelligence at the Foreign Office, made clear the UK shared these anxieties when she spoke to US diplomats at a London arms control meeting in September 2009. The Pakistanis were worried the US “will drop in and take their nukes”, she said, according to a US cable to Washington. Pakistan was now prepared to accept “nuclear safety help” from British technicians, but only under the auspices of the International Atomic Energy Agency.

The cable said Leslie thought nuclear proliferation was the greater danger to the world, but it “ranks lower than terrorism on the public's list of perceived threats”.

Another senior British official at the meeting, Jon Day, the Ministry of Defence's director general for security policy, said recent intelligence indicated Pakistan was “not going in a good direction”, a view shared in November 2008 by Peter Lavoy, the US national intelligence officer for south Asia, who concluded Pakistan's economy was “in tatters” and the country could “completely lose control of its Pashtun territories over the next few years”. “Pakistan's population is becoming less and less educated, the country lacks sufficient energy and clean water resources to serve its population, and there is minimal foreign investment,” Lavoy said.

The Russians shared concerns that Pakistan was “highly unstable”. Yuri Korolev, from the Russian foreign ministry, told US officials: “Islamists are not only seeking power in Pakistan but are also trying to get their hands on nuclear materials.”

Speaking in February in Washington, he called for the problem of Pakistani nuclear sites to be addressed in ongoing missile control talks, claiming: “Over the last few years extremists have attacked vehicles that carry staff to and from these facilities. Some were killed and a number were abducted and there has been no trace seen of them.” Korolev said: “There are 120,000-130,000 people directly involved in Pakistan's nuclear and missile programmes ... There is no way to guarantee that all are 100% loyal and reliable.”

He claimed extremists were now recruiting more easily: “Pakistan has had to hire people to protect nuclear facilities that have especially strict religious beliefs, and recently the general educational and cultural levels in Pakistan has been falling.”

These fears are expressed in the secret state department files against a backdrop of Pakistani determination to build more nuclear warheads.

A Chinese foreign minister, He Yafei, sought to explain to the Americans why Pakistan was blocking fissile material control talks. At a London meeting in 2009, he said: “The underlying problem ... is that India and Pakistan view each other as enemies. Nuclear weapons are crucial to Pakistan. Indeed, a Pakistani military leader said his army was no match for the Indian army.”

US diplomats in Islamabad were told Pakistan was working on producing smaller, tactical nuclear weapons that could be used on the battlefield against Indian troops. “The result of this trend is the need for greater stocks of fissile material ... Strategic considerations point Pakistan in the direction of a larger nuclear force that requires a greater amount of fissile material, Pakistani officials argue.”

The US conducted its own secret analysis of India's military contingency plans, which are codenamed Cold Start. India has said that if sufficiently provoked, it would mount a rapid invasion of Pakistan.

The US said in a cable that it doubted the Indian army was capable of doing so: “It is the collective judgment of the mission that India would likely encounter very mixed results. Indian forces could have significant problems consolidating initial gains due to logistical difficulties and slow reinforcement.”

But the US ambassador to India, Tim Roemer, warned in February that for India to launch Cold Start, would be to “roll the nuclear dice”. It could trigger the world's first use of nuclear weapons since Hiroshima and Nagasaki.— Dawn-Guardian News Service