IAEA's grasp on Iran improves, not enough: ElBaradei

VIENNA (Reuters) - U.N. nuclear watchdog chief Mohamed ElBaradei said on Friday his agency had made "quite good progress" in clarifying Iran's nuclear program thanks to increased Iranian cooperation, but serious doubts persisted.

"In the last four months, in particular, we have made quite good progress in clarifying the outstanding issues ...," he said in a statement accompanying a new report on Iran's behavior.

"On that score, Iran in the last few months has provided us with visits to many places that enable us to have a clearer picture of Iran's current program. However, that is not, in my view, sufficient," he said.

One crucial requirement, he said, was for Iran to implement the IAEA's Additional Protocol, which allows snap inspections that could verify that Tehran is not engaged in secret bomb work beyond declared civilian atomic energy sites.

"We need to have that authority as a matter of law.

Another issue, he said, was Iran's failure so far to address Western intelligence about coordination between uranium processing, missile warhead design work and high-explosives tests, a file known as "weaponization studies".

"The issue is still critical for us to be able to come to a determination as to the nature of Iran's nuclear program."

He also said Iran should heed U.N. Security Council demands for a suspension of all uranium enrichment activity as a key step to easing mistrust.

But he expressed satisfaction U.N. inspectors had been able to clarify all outstanding past issues about the program, except for weaponization, in the past few months because Iran had provided credible answers earlier withheld.

(Reporting by Mark Heinrich)