The U.N. nuclear agency says Iran has agreed to let the agency expand its probe of Tehran's nuclear activities.

The U.N.'s International Atomic Energy Agency says the two sides signed off this weekend in Tehran on "seven practical measures" to be implemented by Iran by May 15.

The IAEA statement gave no details Sunday.

The agency suspects that Iran worked secretly on nuclear arms, something Tehran denies. Their investigation has been stalled for more than six years.

But the IAEA hopes to make progress under an agreement signed with Tehran in November that foresees a step-by-step approach to unresolved questions, starting with less sensitive issues and progressing to the arms-related queries.

The talks are separate from negotiations between Iran and six world powers on Tehran's known nuclear programs.