The US has approved a visa for the Iranian President, Mahmoud Ahmadinejad, to address the UN Security Council when it votes on additional sanctions against Iran.
Washington and Tehran do not have diplomatic relations, but the US, as host country of the UN, is obliged to allow foreign leaders to speak at the Council.
The 15-member Council is to meet on Wednesday to discuss the sanctions against Iran following its refusal to give up uranium enrichment.
Tehran says its programme is for peaceful purposes only and is not aimed at producing nuclear weapons.
