The 3.67% level is that deemed suitable for generating civilian nuclear energy. Above that would mark the first step in a process that could eventually be put to producing the more highly refined material that can be used for a nuclear warhead. Iran has always denied it has any plans to develop an atom bomb.
"Our next step will be enriching uranium beyond the 3.67% allowed under the deal," Zarif said, according to the state-run Iranian broadcaster IRIB. "The Europeans have failed to fulfill their promises of protecting Iran's interests under the deal."