Iran to free U.S. academic on bail: source

TEHRAN (Reuters) - A U.S.-Iranian academic detained in Iran on security-related charges since May will be freed once bail of 3 billion rials ($320,000) has been paid and may be released as early as Tuesday evening, a judiciary source said.

In a case that has further stoked tension with Iran's old foe, the United States, Haleh Esfandiari was arrested in early May during a visit to see her elderly mother in Tehran.

Iran has accused her and another dual national it is holding of involvement in what it says is a U.S.-led plot to topple the Islamic Republic's clerical establishment in a "soft revolution". Washington has dismissed the allegation.

"The amount of bail has been announced to her lawyer and as soon as it is paid, she will be freed," a source in the judiciary spokesman's office told Reuters.

"If all the paper work is finished by the end of today's office hours she will be freed by tonight," the source said.

One of Esfandiari's group of lawyers said he had yet to be informed about the development.

On August 12, Iran's judicial authorities said they had completed their investigations into Esfandiari and another detained Iranian-American, Kian Tajbakhsh. A third U.S-Iranian is also being held while a fourth is already out on bail.

Last month, Iranian television aired "confessions" by Esfandiari and Tajbakhsh, which the Foreign Ministry said had revealed a U.S.-backed plot to overthrow Iran's clerical rulers.

The United States denounced the broadcast as illegitimate and coerced, urging Tehran to release the detainees.

The two countries, which have not had diplomatic ties since shortly after the 1979 Islamic revolution, are also embroiled in an escalating standoff over Tehran's nuclear program. The West suspects it is aimed at making bombs, a charge Iran denies.

News of Esfandiari's bail terms came as Iran and the U.N. nuclear agency watchdog held a second day of talks in Tehran meant to defuse the nuclear dispute.

May's detentions coincided with what rights groups and diplomats said was a fresh crackdown on dissent in Iran, which some analysts have said is a bid to quash opponents when the country is under outside pressure.

Iran dismisses accusations it is violating human rights and insists the cases are purely a legal matter concerning state security.

Esfandiari works at the U.S. Woodrow Wilson International Center for Scholars. Tajbakhsh is a consultant with the Soros Institute, founded by billionaire investor George Soros.