Iranian media said the head of Iran's nuclear agency has resigned.
The ISNA news agency said Gholam Reza Aghazadeh gave no reason Thursday for his resignation as chief of Iran's Atomic Energy Organization. The report said he also resigned from his post as a vice president to Iranian President Mahmoud Ahmadinejad.
ISNA quoted Aghazadeh as saying he submitted a resignation letter almost three weeks ago, adding that Mr. Ahmadinejad accepted it.
Aghazadeh has ties to defeated presidential candidate Mir Hossein Mousavi, who claims officials rigged Mr. Ahmadinejad's re-election in June.
Iran pressed ahead with its nuclear program under Aghazadeh.
The United States and its Western allies fear Iran is trying to develop nuclear weapons. Iran says its atomic activities are for peaceful, civilian use.
On Wednesday, U.S. Secretary of State Hillary Clinton said the United States remains ready to engage with Iran, but warned that the opportunity will "not remain open indefinitely."
She said the United States watched the energy of Iran's election with great admiration, but was "appalled" by the government's violent crackdown against demonstrators protesting President Mahmoud Ahmadinejad's disputed re-election.
Clinton said the government tried to hide its actions by arresting foreign nationals, expelling journalists and cutting off access to technology. She described those actions as "deplorable and unacceptable." She also said those actions have changed the way Iran is viewed internationally.
Some information for this report was provided by AFP, AP and Reuters.