An Iranian opposition leader says that Iranians have dubbed their government the "godfather" of the Islamic State (IS) militant group.
Maryam Rajavi, president of the Paris-based National Council of Resistance of Iran, said Tehran wanted nuclear weapons to foster Islamic extremism, in videoconference testimony before a U.S. House subcommittee in Washington.
The council is part of an umbrella group that includes the Mujahedin Khalq Organization (MKO), which was removed from the State Department list of terrorist groups in 2012.
The council's past and Rajavi's planned testimony in Congress led to controversy, with two former State Department officials reportedly refusing to appear at the hearing.
Rajavi warned against giving Iran too many concessions in negotiations over its nuclear program, saying it would embolden its leaders to be more aggressive in meddling in other countries.
The United States and five other countries in talks with Iran must demand that it completely stop enriching uranium and shut down its nuclear sites and missile programs, she said.
"None of the sanctions should be lifted before an agreement has been signed that effectively and definitively denies the mullahs the bomb," Rajavi said.
"Otherwise, the regime will spend billions of unfrozen assets to buy weapons, including advanced missiles from Russia."