Iran says it has lodged a complaint with the commission responsible for overseeing the implementation of the 2015 nuclear agreement over U.S. sanctions imposed on the country last month.

Parliament speaker Ali Larijani disclosed the complaint on August 1, saying Tehran accused Washington of breaching the accord, known as the Joint Comprehensive Plan of Action (JCPOA), between Iran and six world powers, including the United States.

Iran's complaint came after the U.S. Treasury late last month imposed sanctions on six Iranian firms for their role in developing ballistic missiles after Tehran launched a rocket capable of putting a satellite into orbit.

The U.S. Congress also enacted legislation imposing new sanctions on Iran targeting the missile program, rights abuses, and the Islamic Revolutionary Guards Corps.

"Iran has complained to the commission for the breach of the deal by America," Iran's Tasnim news agency quoted Larijani as saying.

He was referring to the JCPOA Joint Commission set up by the six world powers, Iran, and the European Union to police possible violations of the nuclear agreement.

If the commission is unable to resolve a dispute, parties may turn to the UN Security Council.

Iran has previously accused the United States of defying the spirit of the nuclear deal by imposing sanctions, but has not previously taken any formal action against Washington.

The United States, in imposing the sanctions, has maintained that Iran's missile tests violate the "spirit" of the deal and the UN resolution carrying it out, which calls on Iran to refrain from testing missiles that have the capability to carry nuclear weapons.

U.S. Secretary of State Rex Tillerson repeated that position in a news conference on August 1, saying Iran is violating the spirit of the deal because it calls on Tehran to stop ballistic-missile tests and be a "good neighbor" to other nations in the Persian Gulf region.

​Nonnuclear Sanctions

The central trade-off of the nuclear agreement is the lifting of international sanctions against Iran in exchange for curbs on its nuclear activities. But the United States has maintained nonnuclear sanctions against Iran targeting missile development and other activities.

Tillerson also said that he is a strong backer of the nuclear deal and has had to defend it in discussions with President Donald Trump, who has repeatedly said he would like to ditch the deal.

Tillerson said that he has argued within the Trump administration that the nuclear deal can be used to help rein in Iran's other activities in the Middle East which Trump opposes, including its backing of the Syrian government in a six-year civil war, its support for Lebanon's Hizballah, and its backing of Huthi rebels in Yemen.

"There are a lot of alternative means with which we use the agreement to advance our policies and the relationship with Iran, and that's what the conversation generally is around with the president," Tillerson said.

"The greatest pressure we can put to bear on Iran to change their behavior is a collective pressure" made possible by the agreement, he said.

Still, Tillerson acknowledged that he is not sure he has convinced Trump to stick with the deal in the long run.

"He and I have differences," he said. Trump could still "tear it up and walk away," or he could opt to stay in the deal and hold Iran accountable to its terms.

With reporting by AP and Reuters