Iran's top leader, Ayatollah Ali Khamenei, has banned direct talks with the United States because of what he described as "countless harm" to Iran's interests.
Addressing elite Revolutionary Guard commanders in Tehran Wednesday, Khamenei said direct negotiations with Washington open the way for U.S. "penetration" of the Islamic Republic.
Although he supported the last 18 months of negotiations, Khamenei has not publicly endorsed Tehran's historic nuclear agreement with the United States, France, Britain, China, Russia and Germany that settled a standoff of more than a decade.
Hardliners have accused the administration of President Hassan Rouhani of seeking a resumption of ties with Washington.
Hardline lawmakers also have threatened to impeach Foreign Minister Mohammad Javad Zarif for a historic handshake with President Barack Obama in New York last month.