An Iranian scientist who Tehran claims was abducted by US spies surfaced Tuesday in Washington, where officials confirmed he had been in the United States "for some time" but said he was was free to leave.

It was the latest twist in a bizarre saga tied to international pressure over Tehran's controversial nuclear program, which Iran says is for peaceful purpose, but many nations fear masks a weapons drive.

Iran says US agents kidnapped Shahram Amiri after he arrived in Saudi Arabia for a pilgrimage last year, but speculation has mounted that he defected and was working with the Central Intelligence Agency.

US officials denied kidnapping the Iranian, even as several Internet videos emerged in June featuring a man purporting to be Amiri who claimed to have escaped from US agents in Virginia.

On Tuesday, Amiri was holed up at Iran's consular mission in a non-descript office building in Washington, and US officials confirmed for the first time that he was in the United States.

"He's free to go. He was free to come. These decisions are his alone to make," Secretary of State Hillary Clinton told reporters.

She contrasted the case to that of three young American hikers, who have been held in Iran for nearly a year after allegedly straying into the country during a hiking trip. She renewed calls for their release.

State Department spokesman Philip Crowley said Amiri had planned to return Monday to Iran but could not complete all the arrangements in time to transit through a third country.

"He's been here for some time, I'm not going to specify for how long, but he has chosen to return," Crowley said.

Crowley refused to comment on whether Amiri had provided intelligence but said that the United States had been in contact with him.

An Iran watcher who has contacts with the US administration told AFP that Amiri, who is in his early 30s, had defected and moved in the Sun Belt city of Tuscon, Arizona, but that his family in Iran apparently came under pressure.

"He wasn't a real big fish. He oversold himself. He was debriefed and then allowed to go live in Tuscon," said the academic, who requested anonymity to discuss sensitive information.

"He had illusions of what life as a defector might be like. But he realized that the future didn't look bright as he doesn't know the language and was all alone," he said.

The expert believed that Iran allowed him to return in exchange for telling stories that would benefit the regime of abduction and torture at the hands of the arch-enemy United States.

"This is nonetheless a botched operation by the CIA," the expert contended. "What happens if they want to get another defector out?"

US television network ABC reported first reported Amiri's defection in March and quoted officials saying it was an "intelligence coup" in efforts to undermine Iran's nuclear program.

Amiri told Iranian media he had asked "for a quick return to Tehran." He said he was under intense "psychological pressure" and was constantly watched by "armed people."

"After the release of my interview on the Internet and the disgrace for the American government over this abduction, they wanted to quietly return me to Iran by some country's airline, so that while denying the whole thing they can put a cap on the abduction," he told Iranian state television.

"But in the end they couldn't. Since the day of the release of my remarks on the Internet, the Americans have seen themselves as losers in this saga," he said.

"I am not free and I'm not allowed to contact my family. If something happens and I do not return home alive, the US government will be responsible," the man said, insisting he had not "betrayed" Iran.

There was no sign of the mysterious scientist at the Iranian interests section in the United States, which is under the auspices of the Pakistani embassy in the absence of diplomatic relations between Washington and Tehran.

Secret Service agents waited outside in squad cars with engines running and patrolled a park adjacent to the mission, which lies in a little-marked office building near the upscale Georgetown area.

Officials inside the mission confirmed that Amiri was inside but politely tried to shoo away waiting reporters, who cast a careful eye on each vehicle with tinted windows leaving the building's underground garage.

Prior to his disappearance, Amiri worked in Tehran's Malek Ashtar University of Technology which is believed to be close to Iran's elite Revolutionary Guards.

On a visit to Madrid, Iranian Foreign Minister Manouchehr Mottaki called for the United States to allow Amiri's immediate return.

"We hope that, without any obstacle, he can return to his country, that they do not create any obstacle for his return to his homeland," he told a news conference.

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