Iranian President Mahmoud Ahmadinejad said on Thursday he was ready to debate the men running for US president when he visits New York for the UN General Assembly, and dismissed Western threats of more sanctions over Tehran's nuclear drive.

The outspoken president, who caused a storm of controversy during a visit last year, said: "I am ready for a debate with the US presidential candidates over global issues in the presence of the media at the UN headquarters.

"I have no plans in my schedule to meet with US politicians," he told a press conference.

"Last year, I said I was ready to meet with (President George W.) Bush. But now he is at the end of his term and (a meeting) will not impact our relations and future."

The campaign of Republican candidate John McCain has castigated Democrat rival Barack Obama for offering to negotiate with the leaders of US foes like Iran and Syria if he is elected, and has adopted a hawkish foreign policy.

Obama has said UN sanctions and diplomacy over Tehran's nuclear programme must be made to bite.

Turning to that key point of tension between the two countries, Ahmadinejad said Iran has no fear of threatened new international sanctions over its refusal to halt controversial nuclear work.

"Those who want to impose sanctions are demonstrating their helplessness," he said.

His comments came ahead of a meeting on Friday of six world powers that have offered Iran incentives to freeze uranium enrichment, the process at the heart of Western fears it is seeking atomic weapons.

The White House warned Iran on Monday that it faces possible new sanctions after a new report by the UN atomic watchdog that Tehran had not halted enrichment and was still stalling a UN investigation into its nuclear work.

"Let them impose sanctions against us ... The more they impose sanctions, the more we thank God," Ahmadinejad said. "A country that owns nuclear energy, stem cells, aerospace industries ... does not need these countries."

Iran, which insists that its nuclear programme is geared solely towards energy generation, is already under three sets of UN sanctions over its refusal to freeze enrichment.

The process makes nuclear fuel but in highly extended form can produce the fissile core of an atomic bomb.

Ahmadinejad's visit to New York for last year's UN General Assembly meeting stirred controversy when the outspoken president dismissed talk of war against Iran as "propaganda" and combatively took on US critics who accuse him of denying the Holocaust and of backing terrorism.

He insisted that the Islamic republic had every right to pursue a civilian nuclear programme and said "we are a peace-loving nation."

In a tense exchange at New York's Columbia University, he drew jeers from students for stating that his country had no homosexuals.