Iranian President Mahmoud Ahmadinejad, seen in February, is scheduled to address the UN General Assembly on Sept. 25. ((Mehdi Ghasemi/Associated Press))

Washington has reluctantly granted a visa for Mahmoud Ahmadinejad to address the UN next week, but a Republican presidential candidate says the Iranian president should insteadbe handed an indictment.

The White House said Ahmadinejad was given the visa for travel to the United States, but will not bepermitted to go more than 40 kilometres from the UN headquarters in New York City.

Both the invitation to address the General Assembly on Sept. 25 and the U.S. government's decision to allow Ahmadinejad into the country drew fire from U.S. Republican presidential candidate Mitt Romney.

"If President Ahmadinejad sets foot in the United States, he should be handed an indictment under the Genocide Convention," he wrote in a letter to UN Secretary General Ban Ki-moon on Monday.

Romney cited Ahmadinejad's much-publicized verbal attacks on Israel, support for the Lebanese-based militant organization Hezbollah and his "pursuit of nuclear weapons capabilities."

Ahmadinejad will leave for New York on Sunday, give his address and then return to Iran on Sept. 29, the Associated Press reported.

He has addressed the General Assembly twice before. His speech in September of 2006 included attacks on the U.S. and Britain for their policies opposing Iran's nuclear program.

The United Nations' 62nd General Assembly convened on Tuesday.

With files from the Associated Press