As a team of inspectors from the International Atomic Energy Agency heads to Iran to oversee on Monday, Jan. 20, the dismantling of Iran’s 20% enrichment cascades, the US diplomat who was asked by the president to try to start a bilateral channel with Iran to advance a nuclear agreement has to date said little about his role.

But in an exclusive interview with Al-Monitor on Jan. 14, Deputy Secretary of State William Burns spoke for the first time about the back channel to Iran that he led, which gained momentum after Iran’s election of President Hassan Rouhani in June, and culminated in November with the first agreement to halt the expansion of Iran’s nuclear program in a decade.

Burns, only the second career foreign service officer to be confirmed as deputy secretary of state, credits a team of US and foreign diplomatic colleagues, some who have gone largely unsung, for the success of the effort. Among those Burns singled out for praise were top State Department non-proliferation adviser James Timbie, “truly a national treasure,” and EU foreign policy chief Catherine Ashton, who has led the negotiations on behalf of six world powers with Iran, “an enormously skillful diplomat.”

He also credits the tough-minded professionalism and “clear sense of purpose” of the Iranian nuclear negotiating team put in place after Rouhani, in August, appointed Iran’s former UN envoy Mohammad Javad Zarif as his foreign minister, tapping him to oversee Iran’s nuclear negotiations. “The issues remain very complicated ones,” Burns said. “Having said that, I certainly found the Iranian officials with whom we worked to be quite skillful, quite professional, and I think determined in what they see to be the best interests of Iran in trying to reach a negotiated resolution. That makes for a set of tough negotiations. But I have a good deal of professional respect for the people with whom our team and I were meeting."