According to the "Wall Street Journal," U.S. President Barack Obama secretly wrote Iran's Supreme Leader Ayatollah Ali Khamenei in October about fighting Islamic State (IS) militants in Iraq and Syria.
The newspaper reported on November 6 that Obama stressed that any cooperation was tied to an agreement being reached over Iran's nuclear program by November 24.
The letter is at least the fourth time that Obama has written to Khamenei.
White House Spokesman Josh Earnest did not confirm or deny the report in a briefing with reporters, but said that policy toward Iran remains unchanged.
Obama said on November 5 that the United States presented Tehran with a "framework" that would allow Iran to develop its "peaceful energy needs" and that the Islamic Republic has abided by the interim rules of the agreement.