"Are we going to be able to close this final gap so that (Iran) can reenter the international community, sanctions can be slowly reduced and we have verifiable, lock tight assurances that they can't develop a nuclear weapon," Obama told CBS News in an interview broadcast today.
"There's still a big gap. We may not be able to get there."
His remarks came as America's top envoy, Secretary of State John Kerry and Iran's Foreign Minister Mohammad Javad Zarif started talks today in Oman, the latest diplomatic effort ahead of a November 24 nuclear deal deadline.