The White House is not denying or confirming a newspaper report saying President Barack Obama sent a letter to Iran's supreme leader, Ayatollah Ali Khamenei, on the fight against the Islamic State.
Spokesman Josh Earnest said Thursday he is in no position to discuss private correspondence between the president and any world leader.
But Earnest said U.S. policy toward Iran has not changed and that the United States will not cooperate militarily or share intelligence with Iran.
The Wall Street Journal reported that the president wrote to the Iranian leader last month and spoke of their shared interest in fighting the Islamic State.
Obama told a White House news conference Wednesday that the U.S. and its P5 plus 1 allies have handed Iran a framework for a nuclear agreement.
He calls the framework a progressive step-by-step verifiable way for Iran to get out from under crippling sanctions and rejoin the international community.
Obama, however, called it an "open question" as to whether the Iranian leadership will do what is best for its country and the world.
Iran and the P5 plus 1 (the five permanent United Nations Security Council members and Germany) face a November 24 deadline for a nuclear deal.
Iran would curb its uranium enrichment program in exchange for an end to sanctions. Iran denies wanting to build a nuclear bomb.