Addressing members of civil society during a town hall meeting in Islamabad, US Secretary of State Hillary Clinton said there is a need for Pakistan to remove the world community’s concerns over its nuclear programme.
"The problem with Mr A Q Khan raises red flags for people around the world, not just in the US, because we can trace the export of nuclear information and material from Pakistan through all kinds of channels to many different countries," she said.
Clinton was referring to the disgraced Pakistani scientist who was behind a clandestine network that proliferated nuclear secrets to countries like North Korea and Libya.
She pointed out that Pakistan is the "only country standing in the way of the Conference on Disarmament of the world pursuing the Fissile Material Cut Off Treaty".
She added: "So people say why would Pakistan be the only country not agreeing?"
The FMCT is a proposed international treaty to prohibit the further production of fissile material for nuclear weapons. Last year, Pakistan blocked the Conference on Disarmament from implementing its agreed programme of work despite severe pressure from the major nuclear powers.
Clinton said anyone dealing with Pakistan with the "hope of reaching an agreement that could support civil nuclear power has to answer these questions".
Questions raised by people across the world and the International Atomic Energy Agency "must be answered" by Pakistan, the top US diplomat said.
During a separate interaction with a panel of television anchors, Clinton said the US administration will work with the Pakistan government on civil nuclear energy but the process will take time.
"It took years to do it with India but we are committed to pursuing it and trying to overcome the obstacles that might stand in the way...," she said.