Iran's intelligence ministry has accused a prominent Iranian-American academic of trying to overthrow the country's Islamic system of government.
Haleh Esfandiari is one of the leading US experts on Iran
Haleh Esfandiari, who works for a research institute in Washington, was detained in Tehran earlier this month.
Mrs Esfandiari had gone to Iran in December, but was not able to leave after her passport was stolen.
Her husband has told the BBC that she was only involved in innocent academic activities such as conferences.
The US government described the accusation as "silly" and "outrageous" and called for her immediate release.
In a statement published by the ISNA news agency on Monday, the Ministry of Intelligence said the 67-year-old director of the Woodrow Wilson Centre had confessed during interrogation that her institute was funded by the Soros Foundation.
The ministry said the foundation had "played key roles in intrigues that have led to colourful revolutions in former Soviet republics in recent years" and now aimed to overthrow Iran's government.
"In primary interrogations, she reiterated that the Soros Foundation has established an unofficial network with the potential of future broader expansion, whose main objective is overthrowing the system," it said.
The ministry also said that, with Mrs Esfandiari's help, it had been able to identify the representative of the Soros Foundation in Iran and issued an arrest warrant for him.
Mrs Esfandiari's husband, Shaul Bakhas, an Iranian-born academic now based in the US, said he was shocked by the charges against his wife.
"It's obviously very disturbing that the Iranian government would wish, quite falsely, to implicate my wife in attempts to overthrow the government," he said.
"Nothing could be further from the truth."
"At the same time it seems to me they are reading into innocent activities, such as conferences and meetings and exchanges of scholars, pernicious intent which is not there."
Mr Bakhas also said the only contact with his wife had been several short phone-calls to her elderly mother, who lives in Tehran.
The Nobel Peace Prize-winning lawyer, Shirin Ebadi, has tried to represent Mrs Esfandiari, but she said on Friday that Iran's judiciary was preventing her from doing so.
The BBC's Frances Harrison in Tehran says Mrs Esfandiari's arrest has sent shockwaves through the Iranian diaspora, who were encouraged by the government to return to Iran during the reformist period.
The intention of the authorities seems to be to try and reduce contacts between Iranian intellectuals and the outside world, our correspondent adds.