U.S. President Barack Obama said on Monday an unsettled political situation in Iran may be complicating efforts to seal a nuclear fuel deal between Tehran and major world powers, Reuters reported.

Obama told Reuters in an interview that the United States had made more progress toward global nuclear non-proliferation in the last several months than in the past several years.

"But it is going to take time, and part of the challenge that we face is that neither North Korea nor Iran seem to be settled enough politically to make quick decisions on these issues," he told Reuters in an interview at the White House.