The head of the International Atomic Energy Agency says his probe of allegations that Iran tried to make nuclear arms is at "a dead end" because Tehran is not cooperating. He is also critical of Iran for trying to change a plan endorsed by six world powers. That plan would delay Tehran's ability to make such weapons by committing it to ship out most of its enriched uranium and have it returned as nuclear fuel. IAEA chief Mohamed ElBaradei spoke at the start of the IAEA's 35-nation board meeting.