Calling for restraint in developing nuclear weapons, the US warned that speculation about the potential use of such weapons will not help reduce tensions between India and Pakistan, media reported.
At a news briefing, US State Department spokesman John Kirby stressed the need for exercising restraint in developing nuclear weapons, Dawn reported.
"Obviously, we continue to urge all nuclear-capable states, including Pakistan, to exercise restraint regarding furthering their nuclear capabilities," he said.
He refused to get dragged into a media debate, claiming that some Pakistani officials had threatened to use the nuclear option if the current situation in South Asia led to an armed conflict with India.
"I haven't seen those comments, so I'd be loath to specifically address them," Kirby said, "what we want to see are the tensions decrease".
Asked if the US was working with Pakistan to bring it into the mainstream on the nuclear issue, Kirby said: "Obviously, these kinds of matters are matters we discuss with Pakistani leaders on a routine basis."
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The nuclear issue, he said, was something that the US would continue to focus on, as it was consistent with President Obama's vision of a world without nuclear weapons.
Kirby said the US regularly held discussions with Pakistani officials on the country's nuclear programme but he refused to comment on a US think-tank report that Pakistan would have the third-largest nuclear stockpiles after the United States and Russia in a decade. "I'm not going to have anything substantive to offer on the report's findings," he said.
The think tank report released on Thursday said that Pakistan should have the rights and obligations of a nuclear-weapon state recognised by the NPT.
Countries recognised as nuclear-weapon states by the members of the Non-Proliferation Treaty (NPT) are allowed to keep their weapons in return for meeting certain obligations.
"It is in Pakistan's national security interests and the interests of the international community to find ways in which Pakistan can enjoy the rights and follow the obligations of other nuclear-weapon states recognised by the NPT," says the paper released by two think tanks, the Carnegie Endowment for International Peace and the Stimson Centre.