The National Intelligence Estimate that claimed Iran stopped their nuclear weapons program in 2003 received another blow to its credibility as the United Nations revealed it has documents from the Iranians themselves that show them working on a bomb months after the NIE says they stopped:

In the technical briefing Monday with diplomats from IAEA member states, Heinonen offered new details about the Iranian documents, according to notes obtained by The Washington Post. He revealed that the IAEA had collected corroborating evidence, from the intelligence agencies of several countries, that pointed to sophisticated research into some key technologies needed to build and deliver a nuclear bomb.

Some of the documents, for example, described studies on modifying Iran's Shahab missile to allow it to accommodate a large warhead, which would detonate 600 meters above its target. The feature would make sense only if the warhead was nuclear, Heinonen suggested. Iran now faces a tougher challenge in convincing the world that it has never sought nuclear arms, according to a nuclear weapons expert who reviewed the briefing notes.

"The information is much harder to refute," said David Albright, a former U.N. weapons inspector and president of the Washington-based Institute for Science and International Security.

"It seems to point to work on nuclear weapons -- even if the program wasn't coherent and even if a decision was never made to actually build a weapon."

Iranian documents obtained by the United Nations' nuclear watchdog strongly suggest that Iran was working on a nuclear weapons design as recently as four years ago, U.N. officials disclosed last week in a private briefing.

The documents suggest that Iran's research on nuclear weapons continued for several months after U.S. intelligence officials say the effort was suspended, the International Atomic Energy Agency's top nuclear security expert told diplomats in Vienna, according to notes taken by a participant.