The International Atomic Energy Agency says it has “credible” information that Iran has engaged in activities aimed towards the development of nuclear weapons.

In a report released in Vienna Tuesday, the U.N. agency says the information “indicates” that Iran has worked on the “design” of a nuclear weapon, including the “testing of components.”

The report says Iran appears to have carried out weapon-related nuclear activities as part of a “structured” program prior to 2003. It says Iran may still be engaged in relevant research.

Iranian President Mahmoud Ahmadinejad dismissed the report before its' release. He said “the IAEA is just publishing reports provided by American officials.”

The White House said Monday it expected the report to “echo” U.S. concerns that Iran has failed to live up to international obligations. Western nations accuse Iran of trying to develop nuclear weapons under cover of a civilian energy program, a charge Tehran denies.

In a report Sunday, The Washington Post newspaper said IAEA experts and diplomats, who reviewed intelligence on Iran's nuclear program, believe Tehran has been working with a Russian scientist and other foreign experts to develop a device to trigger a nuclear weapon.

The German foreign ministry said Monday that Berlin would call for “greater political and diplomatic pressure” on Tehran if the IAEA report confirmed Western suspicions about a military dimension to Iran's nuclear work.

The U.N. Security Council has imposed four rounds of sanctions on Iran for failing to suspend sensitive nuclear activities that have both military and peaceful uses.