Obama Says He Exchanged Letters with Iran's Rowhani

U.S. President Barack Obama has said he and Iran's new President Hassan Rowhani have exchanged letters, and warned his reluctance to strike Syria had no bearing on U.S. threats of force to thwart an Iranian nuclear bomb.

Obama, in an interview aired on ABC News Sunday, confirmed the outreach to Rowhani for the first time, and said he believed the Syria chemical arms drama showed that diplomacy could work if backed by threats of military action.

Obama was asked on the ABC News "This Week" program whether he had reached out to Rowhani, a moderate conservative elected in June.

"I have. And he's reached out to me. We haven't spoken-- directly," Obama said.

Asked by interviewer George Stephanopoulos whether the contact was via letters, Obama replied : "Yes."

The president was careful to draw a distinction between U.S. behavior over Syria after freezing military action to negotiate a deal with Russia to secure the regime's chemical arms, and Washington's approach to Iran as a nuclear showdown reaches a critical point.

"I think what the Iranians understand is that -- the nuclear issue -- is a far larger issue for us than the chemical weapons issue," Obama said.

"The threat against ... Israel, that a nuclear Iran poses, is much closer to our core interests.

"A nuclear arms race in the region is something that would be profoundly destabilizing.

"My suspicion is that the Iranians recognize they shouldn't draw a lesson -- that we haven't struck (Syria) -- to think we won't strike Iran."

Obama said that on the other hand, the lesson from the showdown over Syria's chemical weapons, should show that "there is the potential of resolving these issues diplomatically."

Washington has repeatedly warned Iran that it has the option of military action, if diplomacy and crippling sanctions do not convince the Islamic Republic to stop short of building nuclear weapons.

Iran denies that its nuclear program has a military use.