The United States has briefed key nations on intelligence that it says shows Iranian atomic weapons work, namely research on getting a missile warhead to explode at an altitude that would maximize the blast of a nuclear explosion, diplomats and analysts told AFP. However, a non-Western diplomat said the US briefing, carried out in various capitals ahead of a meeting in September of the UN atomic watchdog, "looks plausible but there is no hard evidence," namely direct proof of a nuclear warhead project. Iran says its nuclear program is a strictly peaceful effort to develop atomic power in order...