UN Secretary General Ban Ki-moon challenged Iran on Monday to provide proof that its advanced nuclear programmes are for peaceful purposes, DPA reported.
"I encourage the president of Iran to engage constructively," Ban told the month-long review conference of the Nuclear Non- Proliferation Treaty (NPT) that began Monday at UN headquarters in New York and was being attended by President Mahmoud Ahmadinejad.
"Let us be clear: the onus in on Iran to clarify the doubts and concerns about its programmes," Ban said.
He also called on Iran to comply with UN Security Council resolutions and "fully cooperate" with the International Atomic Energy Agency (IAEA).
"I encourage Iran to accept the nuclear fuel supply proposal put forward by the agency," he said. "This would be an important confidence-building measure."
IAEA director general Yukiya Amano made similar remarks to Ahmadinejad, saying that his government has so far failed to clarify that its nuclear activities were solely for peaceful purposes.
Ahmadinejad was the only head of state attending the NPT review. He was to address the body later Monday, and his country's nuclear programme is sure to be a major focus of the discussions as the United States and its allies are pushing for UN Security Council sanctions to punish the Islamic republic over its nuclear activities.
"The world's people look to you for action," Ban told a packed UN General Assembly with government envoys attending the conference held once every five years to assess progress in nuclear disarmament and non-proliferation.
Ban said eliminating nuclear weapons is a possibility, but the UN agenda on disarmament has been "asleep for too long."
"Sixty five years later, the world still lives under the nuclear shadow," Ban said referring to the atomic bomb set off by the United States over Hiroshima, Japan in August 1945, which put an end to World War II in the Pacific. Ban said he will travel to Japan this year to mark the 65th anniversary.
"How long must we wait to rid ourselves of this threat?" he said in an address opening the conference. "How long will we keep passing the problem to succeeding generations?"
Ban proposed a five-point plan to make the NPT conference a success, including a demand for the world's nuclear powers - the United States, Russia, China, France and China - to unequivocably undertake to eliminate their arsenals of nuclear warheads. There are an estimated 23,000 warheads in the arsenals of those five countries and other countries with nuclear capability.
Scores of foreign ministers were also scheduled to deliver their addresses this week.