WASHINGTON — The Obama administration is exploring a deal with Pakistan that would limit the scope of Pakistan’s nuclear arsenal, the fastest-growing on Earth. The talks are the first in the decade since one of the founders of its nuclear program, Abdul Qadeer Khan, was caught selling the country’s nuclear technology around the world.

The talks are being held in advance of the arrival of Pakistan’s prime minister, Nawaz Sharif, in Washington next week. They focus on American concern that Pakistan might be on the verge of deploying a small tactical nuclear weapon — explicitly modeled on weapons the United States put in Europe during the Cold War to deter a Soviet invasion — that would be far harder to secure than the country’s arsenal of larger weapons.

But outside experts familiar with the discussions, which have echoes of the Obama administration’s first approaches to Iran on its nuclear program three years ago, expressed deep skepticism that Pakistan is ready to put limits on a program that is the pride of the nation, and that it regards as its only real defense against India.

The discussions are being led by Peter R. Lavoy, a longtime intelligence expert on the Pakistani program who is now on the staff of the National Security Council. At the White House on Thursday, Josh Earnest, the press secretary, was asked about the talks and broke from the administration’s previous position of refusing to comment.