VIENNA - The UN nuclear agency on Wednesday said Tehran has always been implementing the Iranian nuclear deal, but the agency needs to closely follow the development of the deal.

After the United States announced withdrawal from the Iranian nuclear deal reached in 2015 in Vienna, the International Atomic Energy Agency (IAEA), which is responsible for investigation of Iran's implementation of the deal, made an official statement, saying that Tehran is under the most robust nuclear verification regime according to the Iranian nuclear deal, and the agency can confirm Iran's compliance with the agreement.

"The IAEA is closely following developments related to the Joint Comprehensive Plan of Action (JCPOA)," said the agency, noting "IAEA can confirm that the nuclear-related commitments are being implemented by Iran."

Under the Iranian nuclear deal, Iran scales back its nuclear plan, and in return, the nuclear related international sanctions should be lifted.