Iran is preparing on Sunday to increase uranium enrichment beyond the level set by Tehran in 2015.
Ali Akbar Velayati, adviser to Iran's supreme leader for international affairs, said in a video that "the Americans violated the agreement directly and the Europeans indirectly violated it."
Velayati said that the increase in uranium enrichment to more than 3.67 percent, which is allowed by the agreement "was unanimously approved by all components of the institution."
Iranian President Hassan Rohani threatened on Wednesday Europe, saying his country would "take the next step" in upgrading uranium enrichment on Sunday.
"If you want to express regret and make a statement, you can do it now," Rohani said.