By Arshad Mohammed and Hossein Jaseb
WASHINGTON/TEHRAN (Reuters) - An Iranian nuclear scientist who vanished more than a year ago mysteriously turned up in Washington on Tuesday saying he had been kidnapped, but the United States denied that he was held against his will.
Iran, which is locked in a standoff with the West over its suspected pursuit of nuclear weapons, has repeatedly accused the CIA of abducting Shahram Amiri, who worked for Iran's Atomic Energy Organisation.
Amiri, who went missing during a pilgrimage to Saudi Arabia more than a year ago, appeared at the Iranian interests section of the Pakistani embassy, which represents Iran in the United States because Tehran and Washington have no diplomatic relations.
A man identifying himself as Amiri has variously said in recent videos that he was kidnapped and tortured; that he was studying in the United States; and that he had fled U.S. agents and wanted human rights groups to help him return to Iran.
Amiri was quoted by Iranian state TV on Tuesday as saying "my kidnapping was a disgraceful act for America."
The mystery surrounding Amiri fueled speculation that he may have information about Iran's nuclear program sought by U.S. intelligence. In March, ABC News reported that Amiri had defected and was helping the CIA.
U.S. officials on Tuesday gave no explanation of why he had come to the United States and said he decided to return to Iran of his own volition.
The United States accuses Iran of using its civil nuclear program as a cover to develop weapons. Iran, which has been hit by four rounds of U.N. Security Council sanctions over the nuclear issue, says its program is to generate power.
Intelligence about the program is at a premium for the United States, which fears that a nuclear-armed Iran would threaten its close ally, Israel, as well as oil supplies from the Gulf and friendly nations in Europe.
"My kidnapping was a disgraceful act for America ... I was under enormous psychological pressure and supervision of armed agents in the past 14 months," Amiri, who is in his thirties, was quoted as telling Iran's state TV in a phone interview.
"Amiri has been escorted by American forces to Iran's interests section in Washington," Iran's PressTV said.
UNCLEAR WHY AMIRI CAME TO U.S.
Just what happened to Amiri and how he came to be in the United States remained unclear.
The State Department said the United States did not kidnap Amiri, but it has not addressed whether another country might have abducted him and turned him over.
Secretary of State Hillary Clinton told reporters: "Mr. Amiri has been in the United States of his own free will and he is free to go." She contrasted his situation with that of three U.S. hikers in Iranian custody.
While U.S. officials denied they were looking to swap Amiri for the three Americans arrested near the Iraqi border about a year ago, raising their case in connection with the nuclear scientist suggested they might be interested in an exchange.
In Tehran, Iranian Foreign Ministry spokesman Ramin Mehmanparast said: "We do not think it is the right thing to discuss swapping Shahram Amiri for three Americans who illegally entered Iranian territory."
Amiri surfaced days after last week's Cold War-style spy swap in which 10 people charged in the United States with being Russian agents were exchanged for four held in Russia on charges of spying for the West.
It was not clear what kind of a reception he might get in Iran.
Asked why Amiri was going back, a U.S. official suggested that Iranian authorities might have threatened his family.
"He may well be feeling some pressure from back home. The Iranians aren't beyond using family to influence people. That could be one explanation for his contradictory messages," the official, who spoke on condition of anonymity, told Reuters.
He also sought to cast doubt on Amiri's account, saying the fact that he was free to make videos and to leave undercut his claim of coercion.
"He himself gives the lie to the idea he was tortured or imprisoned. He can tell any story he wants -- but that won't make it true," the official said.
State Department spokesman P.J. Crowley said Amiri had been scheduled to leave on Monday but was unable to make the necessary arrangements.
Crowley said he had no information to suggest Amiri had been mistreated while in the United States. He did not address the possibility of Amiri's mistreatment elsewhere.
Washington severed diplomatic ties with Tehran after Iran's 1979 Islamic revolution.
Under the umbrella of the Pakistani embassy, the Iranian interests section, which is staffed by Iranians, provides consular services including information on travel visas. U.S. interests in Iran are handled by the Swiss embassy in Tehran.
(Additional reporting by Ramin Mostafavi and Robin Pomeroy in Tehran, Zeeshan Haider in Islamabad and Tabassum Zakaria in Washington, Writing by Parisa Hafezi and Arshad Mohammed, Editing by Alan Elsner)