"Iran's two-month deadline to remaining signatories of the JCPOA (nuclear deal) can not be extended, and the second phase will be implemented exactly as planned", atomic agency spokesman Behrouz Kamalvandi was quoted as saying by Tasnim news agency.
President Trump has said repeatedly that his goal in Iran is "no nuclear weapons" and that he does not want war.
He also made it clear that if the remaining parties to the nuclear deal honor their commitments within the 2-month deadline, Iran could reverse the activities and measures that have taken place since May 8 and "return to the first point". The US announced about its withdrawal from a nuclear deal on May 8, 2018 and imposed sanctions on Iran in November that year.
Iran has threatened to go even further in scaling down nuclear commitments by July 8 unless remaining partners to the deal - Britain, China, France, Germany and Russian Federation - help it circumvent USA sanctions and especially enable it to sell its oil.
Stating that the USA is after Iran's isolation and Iranophobia, he said, "Despite what the United States' attempts not to pay the price of violating its commitments, they are paying a very high price today, and there are only a couple of small countries that approve them".
Its top diplomat warned that the world should not open a "Pandora's Box" in the Middle East, as he denounced USA pressure on Iran and called on it not to drop out of the landmark nuclear deal. Agency head Behrouz Kamalvandi added that Iran will continue to allow the UN's International Atomic Energy Agency (IAEA) to monitor its nuclear facilities for now.More news: U.S. tourist dies in Dominican Republic
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The 2015 accord requires Iran to curb its uranium enrichment capacity, capping Iran's stock of low-enriched uranium at 300 kg of uranium hexafluoride enriched to 3.67 per cent or its equivalent for 15 years.
Pentagon announced on Monday deployment of about 1,000 more USA troops to the Middle East, citing concerns about a threat from Iran. "We will keep contact with the United States and Iran and play our role in reducing the tensions and stabilizing the situation", Nishimura added.
Two US officials speaking on condition of anonymity, told Reuters the US was preparing to send additional troops to the Middle East in response to mounting concerns over Iran.
In a Tuesday statement issued in response to a query from VOA Persian, a USA official who declined to be identified, disputed Iran's assertions that it recently successfully targeted a US spy network. The United States has blamed Iran for the tanker attacks, citing as evidence a series of images showing an Iran Revolutionary Guard Corps boat removing an unexploded limpet mine from the hull of the Japanese oil tanker attacked on June 13.
Trump has said repeatedly he is open to talks with Iran's leadership to discuss a better deal.
Iran has denied involvement in the tanker attacks and has accused America of promoting an "Iranophobic" campaign.