Mr Sharafi, the second secretary to the Iranian embassy in the Iraqi capital, was kidnapped two months ago while shopping in Baghdad.
He told the Irna news agency yesterday that he had been interrogated by CIA agents on the extent of Iran's influence in, and operations concerning, Iraq.
"Upon hearing my response about Iran's official relations with the Iraqi government and officials, they continued torturing me," he said.
"Then they attempted to encourage me to cooperate with them by changing their approach. But I told them that they can contact the Iranian embassy in Baghdad for any information, given that I am only a diplomat and cannot act beyond the limit of my legal duties."
But Gordon Johndroe, a White House spokesman, today countered: "The United States had nothing to do with Mr Sharafi's detention and we welcome his return to Iran.
"This is just the latest theatrics of a government trying to deflect attention away from its own unacceptable actions."
And Lou Fintor, the US embassy spokesman in Baghdad, told the Associated Press news agency that "as we have said repeatedly, we were not involved in the abduction, detention or release of this individual".
Yesterday's claims from Mr Sharafi follow heightened tensions between Iran and the US after the latter's president, George Bush, criticised Iran's treatment of the 15 British sailors released on Thursday.
At a news conference yesterday seven of the 15 Royal Navy and Royal Marines personnel told how they were "exploited" as propaganda stooges by the Iranians and subjected to "extremely nerve-wracking" psychological pressures.
Iran has dismissed the claims of the 15 sailors, alleging that they were told what to say by the British government.
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