WASHINGTON, Oct 1: The US presidential debate on Thursday night showed that nuclear proliferation, along with the war on terror, will dominate the White House agenda for the next four years whether the next occupant is a Democrat or a Republican.

The nuclear issue came up for discussion when moderator Jim Lehrer asked the candidates: "If you are elected president, what will you take to that office thinking is the single most serious threat to the national security of the United States?"

"Weapons of mass destruction, nuclear proliferation," said Democratic challenger John Kerry. "I agree with my opponent that the biggest threat facing this country is weapons of mass destruction in the hands of a terrorist network," said President George W. Bush.

"And that's why proliferation is one of the center pieces of a multi-prong strategy to make the country safer," he said. Both Mr Kerry and Mr Bush also agreed that terrorist groups were trying to acquire nuclear weapons and the United States should do whatever it can to thwart these efforts.

Twice during the 90-minute debate, Mr Bush mentioned the dismantling of the A. Q. Khan network to demonstrate his administration's success in preventing nuclear proliferation.

He first talked about the Khan network in his opening remarks while counting his administration's achievements in the war against terror. "Seventy-five per cent of known Al Qaeda leaders have been brought to justice. The Taliban are no longer in power. Libya has disarmed. The A. Q. Khan network has been brought to justice," said Mr Bush.

He went back to the A. Q. Khan network once more while explaining how effective his administration has been in preventing nuclear proliferation. Mr Kerry was more aggressive than Mr Bush in emphasizing the need to curb nuclear proliferation but focused mainly on unsecured nuclear weapons in the former Soviet Union and Russia where, he said, some 600-plus tons of unsecured nuclear material was still lying around.

"At the rate that the president is currently securing it, it'll take 13 years to get it. I will do it in four years," he said. Mr Kerry, who as a senator was associated with a team tasked with securing unguarded nuclear weapons, said once his team intercepted a suitcase in a Middle Eastern country with nuclear materials in it. The black market sale price for this suitcase was about $250 million, he said.

"Now, there are terrorists trying to get their hands on that stuff today," Mr Kerry warned. Mr Bush said his administration started the Proliferation Security Initiative, involving 60 nations in disrupting the trans-shipment of information and weapons of mass destruction materials.

While nuclear proliferation was discussed as a future threat to America, it was Iraq that dominated first of the three presidential debates held at the University of Miami, Florida.

This was also the first presidential debate in the US history in which both candidates devoted most of their time discussing the Middle East and the Islamic world. President Bush spoke of his initiative to bring democracy to the countries of the greater Middle East, a term his administration has coined to include the entire Islamic world, from Pakistan to North Africa.

"I reject the notion that some say that if you're Muslim you can't free, you don't desire freedom. I disagree, strongly disagree with that," said Mr Bush. His opponent, John Kerry, said America needs a new president who can reach out to the Muslim world to make it clear that this is not a war against Islam. "Osama bin Laden uses the invasion of Iraq in order to go out to people and say that America has declared war on Islam," he said.