The head of the International Atomic Energy Agency will visit Teheran this week to push his agency's investigation of Iran's past nuclear activities and to seek additional knowledge of present programs, the IAEA said Monday. IAEA spokeswoman Melissa Fleming said agency director general Mohamed ElBaradei will visit Friday and Saturday to help the agency "provide assurance about Iran's past and present nuclear activities." She provided no other details in an e-mailed statement. The trip comes at a time of growing impatience by the US and its allies about the pace of the IAEA's probe into Iran's past nuclear activities. ElBaradei said last year that he expected to complete the investigation by December 2007. But diplomats who demanded anonymity because their information is confidential have told The Associated Press that agency experts have run into obstacles.