The International Atomic Energy Agency—the UN's nuclear watchdog—has compiled a report suggesting that Iranian scientists may have tested advanced components of nuclear design that would allow them to put nuclear warheads on missiles. The technology in question, a "two-point implosion" device, once mastered, reduces the diameter of a warhead and makes it easier to add one to a missile. In the U.S. and Britain, the very existence of the technology is kept secret. A European government adviser said, "it is breathtaking that Iran could be working on this sort of material," while a nuclear weapons expert called it "remarkable, that before perfecting step one, they are going straight to step four or five." The IAEA has asked Iran to explain the evidence that they are tampering with advanced nuclear design, as well as separate evidence suggesting that a Russian weapons expert helped Iranian technicians master synchronized high-explosive detonations.