Pakistan Foreign Minister Khurshid Kasuri said a powerful new nuclear reactor under construction was "safe in our hands" and would not spark an arms race with India.
The United States has urged Islamabad, its close ally in the "war on terror", not to use the reactor at the Khushab nuclear complex to bolster its atomic weapons capability.
"It's nothing new, the world knows about it, the world knows that it's safe in our hands," Kasuri said in interview on Friday night at a meeting of Asia's top security forum in Kuala Lumpur.
"It's five years old, it's nearing completion now, I don't know the timing," added Kasuri, the first senior Pakistani official to talk about the plant.
International observers reacted with alarm after the Washington Post on Monday reported the reactor's existence, citing the US-based International Institute for Science and International Security.
The group said satellite photos showed the heavy water reactor could produce more than 200 kilograms of weapons-grade plutonium a year. This would be enough to make 40-50 nuclear weapons every year.
Pakistan remains at the heart of an investigation into a nuclear black market headed by its disgraced chief nuclear scientist, Abdul Qadeer Khan, who confessed in 2004 to passing atomic secrets to Iran, Libya and North Korea.
Kasuri, speaking at the Association of Southeast Asian Nations (ASEAN) Regional Forum, did not specify whether or not the new nuclear plant in Pakistan's Punjab province would be used to produce nuclear weapons.
But he insisted that Pakistan had legislation in place to cover its use and that it abided by international regulations.
White House spokesman Tony Snow said this week that the United States was aware of the plans, while another US official said Washington had been tracking it for "several years".
Kasuri dismissed suggestions that new atomic plant could spark a fresh arms race with India, saying: "It's nothing new, it's five years old, if it had caused an arms race that was five years ago, not today." Asked why the giant reactor was needed if Pakistan and India were trying to make peace, he said: "The (nuclear) programme started with India so one might ask them first."
Kasuri said AQ Khan's network had been dismantled and he defended Pakistan's refusal to let other countries question him.
Military ruler President Pervez Musharraf pardoned Khan, who now effectively lives under house arrest.
"The countries with whom we have cooperated know about the level of cooperation that we have extended with AQ Khan," Kasuri said.
"When we have had long questionnaires (about Khan) addressed to us we have responded to them point by point, very meaningfully and effectively."
Meanwhile Kasuri said he was hopeful that senior Indian and Pakistani officials who are set to meet in Dhaka on August one would "not miss this opportunity" to get peace talks back on track.