But documents submitted to the International Atomic Energy Agency (IAEA) on February 25 suggest that Iran continued work on nuclear weapons beyond that date. The material was presented to the IAEA's 35-nation board in Vienna by the IAEA's head of safeguards, Olli Heinonen.
Britain's ambassador to the IAEA, Simon Smith, says the material came from multiple sources and included designs for a nuclear warhead. Smith also says the documents included information on how a nuclear warhead would perform and how it could be fitted onto a missile.
Iran's ambassador to the IAEA, Ali Asghar Soltanieh, angrily denounced the documents as "forgeries."
Meanwhile, Iran's UN ambassador, Mohammad Khazai, has accused an Iranian opposition group of delivering fabricated evidence to Washington.
Khazai told AP that the United States is getting unreliable intelligence from a group called the Mujahedin-e Khalq Organization (MKO). The MKO was allied with Saddam Hussein's regime in Iraq and is listed as a terrorist organization by Iran, the United States, and the European Union.
There was no immediate confirmation about whether the MKO was one of the sources of the alleged evidence. But Mohammad Mohaddesin, a senior official in a coalition of Iranian opposition groups called the National Council of Resistance of Iran, says his organization had presented the IAEA with evidence supporting the charges. The opposition coalition includes the MKO.
Mohaddesin says the evidence given by his coalition to the IAEA proves that the Iranian regime is still working on nuclear weapons and has even accelerated its arms program since 2003.
In particular, Mohaddesin says the evidence proves beyond any doubt that the Iranian regime is working to produce a nuclear warhead in Khojir, a facility on the southeast edge of Tehran.
Mohaddesin told AP that if the Iranian regime is sincere in its claims that it is not trying to produce nuclear weapons, it should open the doors of the Khojir facility to the UN's nuclear inspectors.
The documents emerged after the IAEA announced in a report on February 22 that Iran has been more transparent about its declared nuclear program than in the past.
But IAEA Director-General Muhammad el-Baradei also said that Tehran still is not doing enough to clear up international concerns about whether it also has a secret, undeclared nuclear-weapons program.
"In addition to our work to clarify Iran's past nuclear activities, we have to make sure, naturally, that Iran's current activities are also exclusively for peaceful purposes," el-Baradei said on February 22. "And for that, we have been asking Iran to conclude the so-called Additional Protocol -- which gives us additional authority to visit places, additional authority to have additional documents -- to be able to provide assurances not only that Iran's declared activities are for peaceful purposes, but there are also no undeclared activities."
State media reports in Iran focused on el-Baradei's praise for Iran and the greater transparency it has provided, but widely ignored his plea for increased cooperation from Tehran on current nuclear activities.
That has led to officials in Tehran and Washington issuing conflicting claims about the IAEA report. Iranian officials call it a "victory" for Tehran while, at the same time, U.S. Secretary of State Condoleezza Rice says the report justifies a fresh round of UN sanctions against Iran.
The UN Security Council is expected to vote on a possible third round of sanctions against Iran later this week for its defiance of a council demand that it suspend all uranium enrichment until it has allayed suspicions about its nuclear program.
Iranian President Mahmud Ahmadinejad says the latest IAEA report vindicates Iran. He also has threatened unspecified "decisive reciprocal measures" against any country that supports additional sanctions against Iran.
THE COMPLETE PICTURE: RFE/RL's complete coverage of controversy surrounding Iran's nuclear program.
An annotated timeline
of Iran's nuclear program.