"The demands today [of Iran] ahead of talks with the West are so minimal, that even if Iran accepts all of them it will still be able to continue and make progress with its nuclear program. It must completely cease its enrichment activities inside Iran, including to levels of 3.5 percent," Defense Minister Ehud Barak said a head of Monday's two-day talks in Vienna between Iran and the International Atomic Energy Agency.

The powers "would certainly take it as an encouraging sign" if Iran started to give credible answers to questions the International Atomic Energy Agency has about the nature of its nuclear work, a Western diplomat said.

But failure or success in Vienna "doesn't necessarily predict" such an outcome at the meeting in the Iraqi capital on May 23, the envoy added.

Iran and the powers involved in nuclear diplomacy — the United States, Russia, China, Britain, France and Germany — revived negotiations in Istanbul last month after a 15-month hiatus, and both sides say they hope for progress in Baghdad.

Meanwhile, a drawing based on information from inside the Parchin military site near Tehran, released by The Associated Press on Sunday, shows an explosives containment chamber of the type needed for nuclear arms-related tests.

Last November, the IAEA issued a report that Iran in 2000 had built a large containment chamber at Parchin in which to conduct high-explosives tests that the IAEA said are "strong indicators of possible [nuclear] weapon development."

The Israeli defense minister said that intelligence agencies are familiar with the image, telling Army Radio on Monday that "this diagram is part of the information known to all leading intelligence agencies in the free world for some time."

Barak said the image reaffirms the need to halt Iran's nuclear capabilities.

The computer-generated drawing was provided to The Associated Press by an official of a country tracking Iran's nuclear program who said it proves the structure exists, despite Tehran's refusal to acknowledge it.

The image is based on information from a person who had seen the chamber at the Parchin military site, that official said, adding that going into detail would endanger the life of that informant. The official comes from an IAEA member country that is severely critical of Iran's assertions that its nuclear activities are peaceful and asserts they are a springboard for making atomic weapons.

A former senior IAEA official said he believes the drawing is accurate. Olli Heinonen, until last year the U.N. nuclear agency's deputy director-general in charge of the Iran file, said it was "very similar" to a photo he recently saw that he believes to be the pressure chamber the IAEA suspects is at Parchin.

He said even the colors of the computer-generated drawing matched that of the photo he had but declined to go into the origins of the photo to protect his source.

In Tehran on Sunday, Saeed Jalili, Iran's top nuclear negotiator, said it was up to the Western nations coming to the Baghdad talks to "build trust of the Iranian nation," adding, "Any kind of miscalculation by the West will block success of the talks."

Attempts to get an Iranian comment on the matter were unsuccessful. A copy of the diagram was attached to an email sent to Ali Asghar Soltanieh, Iran's chief delegate to the IAEA, with a note that the AP would be asking for a reaction. Subsequent phone calls over the weekend went to his voice mail.

The technology used for the suspected multipoint explosives trigger experiments is similar to that employed in manufacturing tiny industrialized diamonds, and the IAEA believes former Soviet scientist Vyacheslav Danilenko — an expert in such diamond-making — helped Iran with designing the chamber.

Diplomats say Danilenko has told the agency that he did not work on such a chamber, but his son-in-law, identified by the diplomats as Vladimir Padalko, told the IAEA that the container was built under Danilenko's direct supervision. Repeated attempts by the AP and other media organizations to contact the two men have been unsuccessful since the IAEA revealed Danilenko's suspected involvement in November.

"What one does inside such a chamber is conduct high explosives testing," said Mark Fitzpatrick, director of the Non-Proliferation and Disarmament Program of the International Institute for Strategic Studies. "You are going to make something go boom with maybe 70 kilograms [154 pounds] of high explosives, you need to contain the explosion," he said.

"And particularly if you are using uranium, which is reportedly the case, you want to contain all the uranium dust so there's not any tell-tale, observable signals of that experimentation."

The official who provided the drawing also shared the following information on the chamber:

ORIGINS — Built in the early 2000s by Azar AB Industries Co. in the city of Arak and then transported to Parchin. Both the senior diplomat familiar with the IAEA investigations and Heinonen, the former senior IAEA official, confirmed this. Company officials did not answer calls seeking comment.

SIZE — Volume: 300 cubic meters, or about 10,600 cubic feet. Diameter: 4.6 meters, or 15.09 feet. Length: 18.8 meters, or 61.68 feet. The senior diplomat confirmed the measurements.

EQUIPPED WITH — A vacuum pump used to remove air from the chamber to minimize pressure that could damage the structure during an explosion; a compressor that shoots water into the chamber after testing to flood and clean it; a septic tank that receives the waste; an elevation system to suspend the explosives in the upper part of the chamber during testing; and a neutron detection system outside the explosion chamber to measure neutron emissions. The senior diplomat said these features would make sense, as would such testing, but could not verify they existed, suggesting they may have been added after the Iranians put up the superstructure shielding the chamber from satellite surveillance.

TIME FRAME — The official said the chamber was used for detonation experiments in 2003, 2005 and 2006. Two officials familiar with the investigations said the first date appeared to be valid but they had no information of subsequent experiments. The U.S. believes Iran stopped working on a concerted nuclear weapons program at various sites after 2003, while the IAEA suspects Tehran is continuing some work but in a much less organized way than before 2003.

THE SCIENTISTS — Seyed Ashgar Hashemi-Tabar, described as "an expert in measuring detonation phenomena" and not previously identified. Acting on information from the same official, the AP previously named other scientists allegedly involved as Fereydoun Abbasi, the current head of Iran's nuclear agency, who escaped an assassination attempt in 2010; Darious Rezainejad, who was killed by a car bomb last year; and Reza Ibrahimi.