The much-delayed trial of three young Americans accused of spying against Iran kicks off Sunday, more than 18 months after they were arrested on the unmarked border with Iraq while on a hiking trip.
The prosecution of Sarah Shourd, Shane Bauer and Josh Fattal comes at a time when anti-American rhetoric is at fever pitch in Iran as it marks the anniversary of its 1979 Islamic revolution.
Fars news agency reported the trial will be held in a closed session at a Tehran revolutionary court.
Iran has dismissed repeated pleas by arch-foe the United States for the release of Bauer and Fattal after it allowed the Shourd to return home on bail of around $500,000 last September after more than a year in detention.
She is expected to be tried in absentia.
Shourd, her fiancé Bauer and fellow hiker Fattal say they innocently strayed into Iran from across the unmarked border with northern Iraq when they were detained on July 31, 2009 by Iranian authorities.
Iran has accused them of "spying and illegally entering the country."
Their Iranian lawyer Masoud Shafii denied the charges against them and said he would press for their "innocence" and immediate release.
Shafii said his repeated requests to visit his clients, held in Tehran's notorious Evin jail, had been rejected and he had not seen them since Shourd's release.
"I should have met with Shane and Josh to prepare the defense, but I was not allowed," Shafii told AFP on Saturday. "I have been told I might see them one or two hours before the trial."
"I have studied the case in full detail. The question of spying is irrelevant. There is just the question of illegal entry, which even if it has happened has been inadvertent as the border was unmarked," Shafii said.
"They are not at all at fault," he said, adding that illegal entry is punishable by a maximum three-year jail term which can also been commuted to a fine under the Iranian penal code.
"I'm pretty sure they won't be convicted because it doesn't have any legal justification. Even if they are convicted, (the sentence) shouldn't be for more than what they have already spent in jail."
Shafii said he would appeal any guilty verdict, but did not expect the case to drag on.
He also said Shourd was unlikely to appear in court.
"All the signs indicate that she will not be there. She has prepared a statement which has been delivered to me through the Swiss embassy," he said.
The Swiss embassy represents U.S. interests in Iran as Washington and Tehran have had no diplomatic ties since the 1979 Islamic Revolution and the subsequent storming of the U.S. embassy by revolutionary students.
The trial, initially set for November 6 but later postponed to February 6, coincides with heightening animosity between Washington and Tehran over Iran's nuclear drive, a dispute punctuated by U.N. sanctions and strident remarks from hard-line President Mahmud Ahmadinejad.
Washington has repeatedly called for the release of its three nationals.
Soon after the release of Shourd, U.S. Secretary of State Hillary Clinton said that holding the other two and prosecuting them was baseless.
"We do not believe that there is any basis whatsoever for them to be put on trial and we regret that they and their families are being subjected to a criminal system that we do not think in any way reflects their actions," she said.
"So it's our continuing request to the Iranian government that, just as they released the young woman, that they release these two young men."
The trial is to be presided by Judge Abolqasem Salavati who has overseen a string of prosecutions involving people charged with anti-Iran activities, particularly those connected with huge street protests after the disputed June 2009 presidential election.
He also presided over the trial of French academic Clotilde Reiss, who was arrested during the election unrest and later freed after paying a fine of around $285,000.
In a separate case, Iran is holding two German journalists accused of spying after they were arrested while interviewing the son of a woman condemned to death by stoning for adultery under the country's Islamic laws.
Mystery also shrouds the fate of former FBI agent Robert Levinson who disappeared on the Iranian Gulf island of Kish in March 2007. Iran has denied having any information about the missing American's whereabouts.
In November 2005, Iran arrested French skipper Stephane Lherbier and his German client Donald Klein for straying into Iran's territorial waters during a fishing expedition from the United Arab Emirates across the Gulf.
They said they had been misled by Emirati maps showing the waters as Emirati, but were sentenced to 18 months in jail two months later. The pair were released after serving most of their sentence.