The head of the International Atomic Energy agency voiced regret Monday that little progress had been made in recent months on Iranian cooperation over any possible military dimension of its nuclear program. "It is true that we have had some engagement from Iran on issues with possible military dimension. His remarks come as US Secretary of State John Kerry is to return to Switzerland for talks Thursday with his Iranian counterpart Mohammad Javad Zarif on a deal to restrain Tehran's nuclear program, Kerry's ****** said. The complex deal on the table would likely involve Iran reducing its nuclear activities, allowing tight inspections, and limiting development of new nuclear machinery.