The United States said Wednesday that subversion charges against an Iranian-American academic on trial in Tehran are without foundation and renewed a call for his release.

Dual-national scholar Kian Tajbakhsh is among dozens of people, including prominent Iranian opposition figures, being tried for allegedly fomenting violence after Iran's disputed June 12 presidential election. 

In some of its strongest comments to date on the Iranian dissident trials, the State Department has asserted the innocence of the lone American citizen among the defendants and says that "the world is watching" the spectacle of what have been widely described as show trials.

The Iranian-American, who spent four months in an Iranian prison in 2007, was detained again shortly after the June election.

He appeared in a Tehran courtroom this week among the latest group of Iranian opposition activists and others being tried for allegedly instigating violence in post-election protests of the disputed re-election of Iranian President Mahmoud Ahmadinejad.

Tajbakhsh, a social scientist and urban planner, taught urban policy and politics at the New School for Social Research in New York but has lived in Iran for the past several years as a consultant for Iranian government agencies and non-governmental groups there.

At a news briefing, State Department Spokesman Ian Kelly said Tajbakhsh has been wrongly accused and poses no threat to Iran's government.

"He has not been given a lawyer. We believe that the charges that he's facing are without foundation, and we of course have consistently called for his release," he said. "Mr. Tajbakhsh poses absolutely no threat to the Iranian government or to its national security. He played absolutely no role in the election, and he's a scholar.   He's really devoted his life to promoting understanding between the Iranian and the American people and he's scrupulously stayed politically-neutral."

Kelly said the United States believes Tehran authorities should respect the will of the Iranian people as expressed in the election and respect their fundamental human rights.

He said the world is watching the court proceedings and that the United States "will bear witness" to what is going on.

The Iranian trials have been condemned by Iranian opposition activists and human rights groups, among them Amnesty International, which says the proceedings are grossly unfair and bear all the hallmarks of Soviet-era show trials aimed at deterring dissent.

The Obama administration has denied Iranian charges of U.S. meddling in the Iranian election and its aftermath but has been sparing in its comments about the trials.