VIENNA — The U.N. nuclear monitoring agency presented documents today that diplomats said indicate Iran may have focused on a nuclear weapons program after 2003 — the year that an American intelligence report says such work stopped.

Iran again denied ever trying to make such arms. The chief Iranian delegate to the International Atomic Energy Agency, Ali Ashgar Soltanieh, dismissed the information showcased by the body as “forgeries.”

He and other diplomats, all linked to the IAEA, commented after a closed-door presentation to the agency’s 35-nation board of intelligence findings from America and its allies and other information purporting to show Iranian attempts to make nuclear arms.

A summarized National Intelligence Estimate, made public late last year, also came to the conclusion that Tehran was conducting atomic weapons work. But it said the Iranians froze such work in 2003.

Asked whether board members were shown information indicating Tehran continued weapons-related activities after that time, the chief British delegate to the IAEA, Simon Smith, said: “Certainly some of the dates … went beyond 2003.”

He did not elaborate. But another diplomat at the presentation, who agreed to discuss the meeting only if not quoted by name, said some of the documentation focused on an Iranian report on nuclear activities that some experts have said could be related to weapons.

She said it was unclear whether the project was being actively worked on in 2004 or the report was a review of past activities. Still, any Iranian focus on nuclear weapons work in 2004 would at least indicate interest past the timeframe outlined in the American intelligence estimate.

A senior diplomat who attended the IAEA meeting said that among the material shown was an Iranian video depicting mock-ups of a missile re-entry vehicle. He said the IAEA director general, Oli Heinonen, suggested the component — which brings missiles back from the stratosphere — was configured in a way that strongly suggests it was meant to carry a nuclear warhead.

Other documentation showed the Iranians experimenting with warheads and missile trajectories where “the height of the burst … didn’t make sense for conventional warheads,” he said.

Mr. Smith and the senior diplomat both said the material shown to the board came from a variety of sources, including information gathered by the agency and intelligence provided by member nations.

“The assumption is this was not something that was being thought about or talked about, but the assumption is it was being practically worked on,” Mr. Smith told reporters.

He said the IAEA presented a “fairly detailed set of illustrations and descriptions of how you would build a nuclear warhead, how you would fit it into a delivery vehicle, how you would expect it to perform.”