Iran on Sunday repeated its offer to help the United States in finding an ex-FBI agent who went missing while on a trip to the Islamic republic to probe cigarette counterfeiting in the region.
On Friday the United States, arch-foe of Iran, asked again for Tehran's help in finding Robert Levinson who disappeared six years ago from the Gulf island of Kish.
"We have said many times that we do not have any information in this regard," Foreign Minister Ali Akbar Salehi was quoted as saying by the ISNA and IRNA news agencies.
"We have repeatedly announced that we are ready to cooperate on humanitarian ground to find... how he disappeared."
Salehi said Iran was ready to share intelligence to help locate Levinson.
"We are ready to cooperate through the intelligence entities to shed light on this issue. I once again repeat that this person is not in Iran and the Americans have already acknowledged this," Salehi said.
In 2011 former US Secretary of State Hillary Clinton said Washington had received information that Levinson was in southwest Asia, but called on Tehran to help locate him.
On Friday the US renewed the call.
"The Iranian government previously offered assistance in locating Mr Levinson, and we look forward to receiving this assistance, even as we disagree on other key issues," White House spokesman Jay Carney said.
Levinson's disappearance has become another point of tension between the two arch-foes who are already at odds over multiple issues, including Tehran's controversial nuclear programme.
Mystery shrouds the fate of Levinson, who disappeared from Kish while reportedly investigating cigarette counterfeiting in the region. His wife Christine last heard from him on March 8, 2007.
In January she released photos of her husband wearing an orange jumpsuit similar to those worn by prisoners at the US-run Guantanamo Bay Detention Center in Cuba, holding a white placard that read, "Why You Can Not Help Me."
Salehi said that based on that evidence Levinson "is not in Iran."
The FBI has announced a $1 million reward for information leading to Levinson's safe return.