Iran's president has ruled out any talks with major powers over its nuclear programme, saying the issue is "closed".
"We have said this before and we are saying it right now, that we will not talk about the nuclear issue with those outside the IAEA [International Atomic Energy Agency]," Mahmoud Ahmadinejad said on Monday.
Ahmadinejad did offer to "debate ... on global issues as well as world peace and security" with Barack Obama, his US counterpart, at the UN General Assembly in September.
Obama has urged a "serious process of engagement" with Iran, but last week threatened deeper sanctions if Tehran did not respond positively to attempts to open dialogue over Iran's nuclear agenda.
Western nations, including the US, have accused Iran of planning to develop atomic weapons, but Tehran insists that it only wants the technology for energy production.
Javier Solana, the European Union foreign minister, held talks with Said Jalili, Iran's nuclear negotiator, in April about discussions with the so-called P5-plus-1, which includes the US, Britain, France, China, Russia and Germany.
The group's dialogue with Iran has been on hold since last September.
North Korea denial
Speaking after North Korea tested an atomic weapon on Monday, Ahmadinejad denied any co-operation with Pyongyang on nuclear development and criticised nations which were constructing nuclear weapons.
"In principle we oppose the production, expansion and the use of weapons of mass destruction," he said.
"...all of the countries who have nuclear weapons must enroll in a collective commitment and be disarmed within a clear plan and timetable"
"The worst thing that a government could do would be to spend a nation's resources, which should be spent for people's welfare, to produce and store nuclear weapons.
"We oppose this and all of the countries who have nuclear weapons must enroll in a collective commitment and be disarmed within a clear plan and timetable."
Ahmadinejad made the remarks as he campaigned for the June 12 presidential election, during which he faces a challenge from liberal candidates advocating at least some detente with the US.
Iran has repeatedly rejected calls for it to halt uranium enrichment, a process used to develop fuel for a nuclear reactor, but which call also be used to produce an atomic warhead.
An Israeli foreign ministry document leaked to the media on Monday said that Venezuela and Bolivia were suspected of selling uranium to Iran.
It also claimed that Caracas was helping Tehran skirt UN imposed sanctions.