Iranian Bombshell?

As the U.N. Security Council prepares to debate Iran's nuclear ambitions--perhaps as early as next week--Bush Administration officials are readying a new intelligence briefing for council members on Tehran's weapons programs. It will rely mainly on circumstantial evidence, much of it from documents found on a laptop purportedly purloined from an Iranian nuclear engineer and obtained by the CIA in 2004. U.S. officials insist the material is strong but concede they have no smoking gun.

They do, however, have diagrams that they believe show components of a nuclear bomb. According to a Western diplomat familiar with the U.S. intel brief, a Farsi-language PowerPoint presentation on the laptop has "catchy graphics," including diagrams of a hollow metallic sphere 2 ft. in diameter and weighing about 440 lbs. Other documents show a sphere-shaped array of tiny detonators. No file specifically refers to a nuclear bomb, but U.S. officials say the design of the sphere--an outer shell studded with small chemical-explosive charges meant to detonate inward, which would squeeze an inner core of material into a critical mass--is akin to that of classic devices like Fat Man, the atom bomb dropped on Nagasaki during World War II. "Because of the size and weight and the power source going into it and height-of-burst requirements," says the diplomat, Western experts have concluded that the design "is only intended to contain a nuclear weapon. There's no other munition which would work." A report issued last week by Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA), says Iranian officials have dismissed a number of the laptop documents as fabricated.

Intelligence of this kind helped secure the backing of Russia and China in last month's IAEA vote to refer Iran to the Security Council. Western officials hope the new briefing will win council support for further action; most of them see no viable alternative to U.N. efforts to try to gain Iran's compliance. As a Western diplomat puts it, "There's a military option--but not a military solution."