The condemned woman, Sakineh Mohammadi Ashtiani, is a 43-year-old mother of two who already received 99 lashes after confessing -- reportedly under duress -- for alleged adultery in 2006. A judge later reviewed her case and ordered that she be put to death by stoning.
Her two grown children are campaigning furiously to get authorities to review her case, but say they have gotten nowhere.
Radio Farda and other reports say the imposition of the stoning sentence is "imminent."
State Department deputy spokesman Mark Toner on July 8 said U.S. officials "condemn in the strongest terms the use of the practice of stoning anywhere it occurs as a form of legalized death by torture." He described the process as "barbaric and an abhorrent act."
Toner added that Washington "call[s] on the Iranian authorities to live up to their due process commitments under the International Convention on Civil and Political Rights."
Also on July 8, British Foreign Secretary William Hague said he was "appalled by reports of this imminent execution."
"I think stoning is a medieval punishment that has no place in the modern world, and the continued use of such a punishment in Iran demonstrates, in our view, a blatant disregard for human rights and commitments which [Iran] has previously entered into," Hague told reporters in London.
"I do call on Iran to put an immediate stay to this execution and review the process by which this woman was tried," Hague urged. "And I think if this punishment was carried out, it would disgust and appall the watching world."
Amnesty International, which has repeatedly called on Iran and other countries to stop executions, says it has recorded 126 Iranian executions in the first six months of the year.
The International Campaign for Human Rights in Iran has said Ashtiani was in an abusive marriage that led to the murder of her husband by another man with whom she was said to be involved. Both were given 10-year sentences but Ashtiani was additionally sentenced for the extramarital relationship.
written by Andy Heil based on RFE/RL, Radio Farda, and agency reports