The U.N. nuclear watchdog chief is "positively considering" a U.S. Senate invitation to speak about his agency's monitoring role in Iran following the country's deal with world powers on curbing its atomic activity, a diplomatic source said.

Some members of the U.S. Congress, which will consider whether to approve the deal, have asked for more information to be made public relating to the International Atomic Energy Agency's part in verifying Iran's implementation of the pact.

"I understand that Director General (Yukiya) Amano overnight (Vienna time) received an invitation letter from the members of the U.S. Senate Foreign Relations Committee. I also understand that he is positively considering the invitation," the source, who is familiar with the matter, told Reuters.

Amano has the delicate task to assess Iran's past and future nuclear program. He has no political mandate and never tires of stressing the IAEA's technical role.

He must nonetheless manage and maintain a fine balance between delivering data on Iran's nuclear activities and the major political consequences such information can have.

If Iran were to break its promises made in the historic July 14 deal reached with six world powers, Amano and his inspectors would be responsible for detecting and telling the world about the breach. The nuclear agreement will have to be ratified by the U.S. Congress. It has until Sept. 17 to accept or reject it.

The IAEA said it is normal practice for it not to publish safeguards arrangements with countries and that Iran is no exception, adding that the arrangement it reached with Iran on July 14 meets its requirements to clarify outstanding issues.

U.S. Republicans have objected to the deal as not tough enough to stop Iran obtaining a nuclear weapon in the long run.

At an emotional Senate hearing this week, U.S. Secretary of State John Kerry warned that rejecting the deal would remove all limits on Iran's nuclear work, give it a fast track to a weapon and access to billions of dollars from collapsed sanctions.

Under the July 14 pact, world powers agreed to lift sanctions in return for curbs on a nuclear program the West suspects was aimed at developing the means to build an atomic bomb. Tehran says it seeks only peaceful atomic energy.

By Reuters