The United States on Tuesday denied reports it had offered Iran a prisoner swap to retrieve former U.S. Marine Amir Hekmati, who has been imprisoned in the Islamic republic since 2011.
Iranian media had reported that Hekmati's lawyer asked for his release in return for the freeing of Iranians in the United States.
"Those reports are not accurate," State Department spokesman Jeffrey Rathke told a news conference. "The U.S. government has not proposed a prisoner exchange for Mr Hekmati."
The purported proposal supposedly came through Swiss intermediaries. The United States and Iran have not had official diplomatic relations since 1980.
Rathke renewed calls for Hekmati's release and urged Tehran to free two other Americans, Saeed Abedini, a Christian pastor, and Washington Post journalist Jason Rezaian, and to help find Robert Levinson, a retired FBI agent who disappeared in Iran in 2007.
Relations between traditional foes Washington and Tehran have improved somewhat in recent months and the two countries have had direct exchanges over Iran's nuclear program.
Arrested in August 2011, Iranian authorities convicted Hekmati of spying for America's Central Intelligence Agency.
He was initially sentenced to death in 2012 but Iran's top court subsequently reduced the penalty to 10 years in prison.