The Bush administration is considering taking the unprecedented step of preventing a visiting head of state from addressing the United Nations in New York by denying a visa to Mahmoud Ahmadi-Nejad, Iran's newly elected conservative president,Guy Dinmore reports from Washington. Officials said a decision rested on the outcome of investigations into whether Mr Ahmadi-Nejad was involved in the 1979 US embassy hostage crisis, and the killing of an Iranian-Kurdish dissident leader in Vienna in 1989. Iran denies his involvement in either event. A senior Iranian official yesterday confirmed that Mr Ahmadi-Nejad planned to address the UN Millennium Summit and its annual General Assembly next month. His US visa application is expected to be submitted today.