A senior Iranian nuclear negotiator says the Islamic Republic reserves the right to respond to any US violation of the landmark nuclear agreement signed between Tehran and the P5+1 group of countries.

Iranian Deputy Foreign Minister for Legal and International Affairs Abbas Araqchi made the comments in the Austrian capital of Vienna on Friday at the end of the eighth meeting of the Iran-P5+1 Joint Commission, overseeing the implementation of the agreement, known as the Joint Comprehensive Plan of Action (JCPOA).

“The joint commission conveyed to the world the strong message of support by all members for the implementation of the JCPOA,” he said.

“All [members] emphasized that the JCPOA must be implemented completely with goodwill and any move undermining the successful implementation of the JCPOA must be prevented,” Araqchi added.

At the end of the meeting, Iran announced that it had not been convinced of explanations given about Washington's failures to honor its obligations under the nuclear agreement, the Iranian diplomat said and added, “The US must be held accountable [for its violations of the JCPOA.]”

He noted that all the sides confirmed that Iran is sticking to its side of the pact and hailed the country’s cooperation with the International Atomic Energy Agency (IAEA).

Araqchi further said that the participants discussed the issue of anti-Iran sanctions in details while the Iranian side spoke about the instances of US violations of the JCPOA or foot-dragging in fulfilling its commitments.

Iran and the five permanent members of the United Nations Security Council - the United States, Britain, France, China and Russia - plus Germany signed the JCPOA on July 14, 2015 and started implementing it on January 16, 2016.

Under the agreement, limits were put on Iran’s nuclear activities in exchange for, among other things, the removal of all nuclear-related bans against the Islamic Republic.

The UN Security Council later unanimously endorsed a resolution that effectively turned the JCPOA into international law.

US President Donald Trump has been a virulent critic of the JCPOA signed under his predecessor Barack Obama, calling it "the worst deal ever."

Although Trump certified to Congress that Iran is in compliance with the agreement, his administration on Tuesday announced a fresh round of economic sanctions over Iran's ballistic missile program.

The US Departments of Treasury and State said they are targeting 18 Iranian individuals, groups and networks.

Later in the day, Iran’s Foreign Ministry denounced the US move as “cheap and useless,” saying Tehran would respond with its own sanctions against the Americans.

In a statement, the ministry condemned the US move to add new names to its list of illegal sanctions against Iran and said the Islamic Republic "will in turn impose new sanctions against a number of other American persons and entities that have taken hostile steps against the Iranian people and other Muslim nations in the region."

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