Quoting an Intelligence Ministry statement, state media said May 21 that Haleh Esfandiari and her employer, the Washington-based Woodrow Wilson Center for Scholars, were trying to set up a network "against the sovereignty of the country."
It also accused a New York-based foundation set up by U.S. financier George Soros of being involved in the network.
Esfandiari's husband, Shaul Bakhash, said it was unclear if his wife had been formally charged. He also denied the allegations against her.
"Any implication that my wife was involved in a plan in a revolution -- 'soft' or otherwise -- is totally without foundation," he told The Associated Press.
Esfandiari 'No Threat'
The U.S. State Department also rejected the charges, with spokesman Tom Casey urging Iranian authorities to release Esfandiari.
"Haleh Esfandiari is not a threat to this Iranian government or the regime as a whole," Casey told CNN. "She is an academic and a voice for tolerance and people-to-people exchanges between the Iranian and American people. We can't imagine why she is considered a threat."
He described the allegations against Esfandiari as "absolutely absurd."
Esfandiari was detained on May 8 after returning to Iran in December to visit an elderly relative.
The United States says she is among a number of Iranian-Americans being detained by Tehran.
(AP, AFP, Reuters)