UN Secretary General Antonio Guterres said he is “deeply concerned” over President Donald Trump’s decision to withdraw the US from the 2015 nuclear agreement with Iran, calling on all other nations to support the agreement and preserve the deal.

Trump made the announcement at the White House yesterday and signed a memorandum to begin reinstating economic sanctions on Iran at “the highest level”.

In a statement released shortly afterwards, Guterres said he was “deeply concerned” by the announcement that the US would withdraw from the Joint Comprehensive Plan of Action (JCPOA) and reinstate sanctions on Iran.

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“I have consistently reiterated that the JCPOA represents a major achievement in nuclear non-proliferation and diplomacy and has contributed to regional and international peace and security,” he said.

The JCPOA      reached by Iran, China, France, Germany, Russia, the United Kingdom, the US and the European Union            sets out rigorous mechanisms for monitoring restrictions placed on Iran’s nuclear programme, while paving the way for the lifting UN sanctions against the country.

“It is essential that all concerns regarding the implementation of the Plan be addressed through the mechanisms established in the JCPOA,” Guterres said, adding that “issues not directly related to the JCPOA” should be addressed separately, “without prejudice to preserving the agreement and its accomplishments.”

The UN chief called on other JCPOA participants to abide by their respective commitments and on all other member states to support the agreement.

Earlier this month, the International Atomic Energy Agency (IAEA) released a statement saying that according to its December 2015 Board of Governors report, “the agency had no credible indication of activities in Iran relevant to the development of a nuclear explosive device after 2009.”

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At the Board of Governors meeting in March, IAEA chief Yukiya Amano had said Iran was abiding by the deal and IAEA inspectors had been given access to all sites and locations, upon request.

“If the JCPOA were to fail, it would be a great loss for nuclear verification and for multilateralism,” he said.

The leaders of France, Germany and the United Kingdom have expressed regret and concern over Trump’s decision to withdraw the US from the JCPOA.

In a joint statement from Prime Minister Theresa May, German Chancellor Angela Merkel and President Emmanuel Macron emphasised their “continuing commitment” to the JCPOA.

They urged the US to ensure that the structures of the JCPOA remained intact, and to “avoid” taking action which “obstructs” its full implementation by all other parties to the deal.

“We call on the US to do everything possible to preserve the gains for nuclear non-proliferation brought about by the JCPOA, by allowing for a continued enforcement of its main elements,” they said in the statement.

They also encouraged Iran to show “restraint” in response to the decision by the US.

“Iran must continue to meet its own obligations under the deal, cooperating fully and in a timely manner with IAEA inspection requirements. The IAEA must be able to continue to carry out its long-term verification and monitoring programme without restriction or hindrance. In turn, Iran should continue to receive the sanctions relief it is entitled to whilst it remains in compliance with the terms of the deal,” they said.

The leaders said that according to the IAEA, Iran continued to abide by the restrictions set out by the JCPOA, in line with its obligations under the Treaty on the Non-Proliferation of Nuclear Weapons.

“The world is a safer place as a result. Therefore we, the E3, will remain parties to the JCPOA. Our governments remain committed to ensuring the agreement is upheld, and will work with all the remaining parties to the deal to ensure this remains the case, including through ensuring the continuing economic benefits to the Iranian people that are linked to the agreement,” they said.