U.S. President Donald Trump will not certify that Iran is complying with the terms of a nuclear deal forged in 2015. 

In a speech from Washington, D.C., Trump outlined a history of a "sponsorship of terrorism," pointing specifically to attacks against the United States. 

Trump said the deal was "one of the worst" and most "one-sided transactions the United States has ever entered into" and argued the sanctions lifted by the deal gave the country's leaders a "lifeline" when they were in financial trouble, which was used to fund violence and terrorism. 

He said the deal delivered weak inspections in exchange for no more than a temporary delay in Iran's path to nuclear weapons.  

"Based on the factual record I have put forward, I am announcing today that we cannot and will not make this certification," Trump said.

Although Trump allowed that Iran is living up to the letter of the agreement, he said it was not following the agreement's "spirit" of the regional stability it was intended to encourage.

He said his administration will seek to counter the Iranian regime's destabilizing activities and will impose additional sanctions to block its financing of terrorism. Those sanctions especially target Iran's Revolutionary Guard. 

The new strategy will also seek to address the proliferation of Iran's missiles and weapons, he said, adding that the U.S. will deny Iran's paths to develop nuclear weapons. 

"If we are not able to reach a solution by working with Congress and our allies then the agreement will be terminated," Trump said. "It can be cancelled by me, as president, at any time." 

Under U.S. law, Trump faced a Sunday deadline to notify Congress whether Iran is complying with the accord that was painstakingly negotiated over 18 months by the Obama administration and determine if it remains a national security priority.

"The longer we ignore a threat the more dangerous that threat becomes," Trump said.  

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International Atomic Energy Agency (IAEA) Director General Yukiya Amano says Iran is honouring its commitments. (Heinz-Peter Bader/Reuters)

The chief of the UN agency monitoring the nuclear deal says Iran is honouring its commitments.

The statement from Yukiya Amano of the International Atomic Energy Agency was issued Friday after Trump's speech.

Amano says the "nuclear-related commitments undertaken by Iran ... are being implemented" and Tehran is "subject to the world's most robust nuclear verification regime."

Iran committed to deal

Despite Trump's comments, Iran will remain committed to the nuclear deal as long as it serves the country's national interests, and its ballistic missile program will expand despite pressure from the United States, Iranian President Hassan Rouhani said.

Rouhani said in a live television address that the speech was full of "insults and fake accusations" against Iran.

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Iran's President Hassan Rouhani responded to Trump's speech by saying the country is committed to the multinational nuclear deal as long as it serves the Iran's national interests. (Stephanie Keith/Reuters)

"The Iranian nation has not and will never bow to any foreign pressure ... Iran and the deal are stronger than ever ... Iran's Islamic Revolutionary Guards Corps will continue its fight against regional terrorists," Rouhani said.

He said that Trump's decision to decertify the deal would isolate the United States as other signatories of the accord remained committed to it and the deal was not renegotiable.

Israel, Saudi Arabia back Trump

Shortly after Trump's remarks, he received congratulations from Israeli Prime Minister Benjamin Netanyahu.

"He [Trump] boldly confronted Iran's terrorist regime [and] created an opportunity to fix this bad deal, to roll back Iran's 
aggression and to confront its criminal support of terrorism," Netanyahu said in a Facebook video. 

Saudi Arabia also welcomed what it called Trump's "decisive strategy" toward Iran and said lifting sanctions had allowed Tehran to develop its ballistic missile program, step up its support for militant groups including Hezbollah and the Houthis in Yemen, and attack global shipping lanes.

The Riyadh government said in a statement it had supported the nuclear agreement, "but Iran took advantage of the economic gain from raising sanctions and used it to continue destabilizing the region."

But Trump's decision also faced criticism, with European Union foreign policy chief Federica Mogherini saying the deal is a robust agreement that is working and cannot be terminated by any one leader. 

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European Union foreign policy chief Federica Mogherini saying the deal is a robust agreement that is working and cannot be terminated by Trump. (Craig Ruttle/Associated Press)

Mogherini said the accord "is a robust deal that provides guarantees and a strong monitoring mechanism so that Iran's nuclear program is, and will remain, exclusively for civilian purposes only." 

Mogherini, who worked on behalf of major world powers to secure the deal, told reporters that "there have been no violations of any of the commitments." 

She underlined that Trump cannot kill the deal, saying: "the president of the United States has many powers: not this one." 

European allies, Russia, criticize decision

Also critical of Trump's decision were British Prime Minister Theresa May, German Chancellor Angela Merkel and French President Emmanuel Macron, who issued a joint statement Friday night calling the deal "the culmination of 13 years of
diplomacy" and "a major step towards ensuring that Iran's nuclear program is not diverted for military purposes."

The three leaders urged the Trump administration and Congress to consider the possible consequences for the West's security "before taking any steps that might undermine" the deal, including imposing sanctions on Iran that the agreement lifted.

Russian Deputy Foreign Minister Sergei Ryabkov said on Friday it was "extremely troubling" that Trump was raising questions that had been settled when an international deal on Iran's nuclear program was signed, RIA news agency reported.

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Iranian Revolutionary Guards march in 2008. The group controls large swaths of Iran's economy. (Vahid Salemi/Associated Press)

Former U.S. Secretary of State John Kerry says Trump's decision not to certify is reckless and divisive.

Kerry led the Obama administration's Iran deal negotiations. In a statement Friday, Kerry says Trump is "creating an international crisis."

Kerry says it is now up to Congress and the other parties to the deal to be "the adults in the room" and save it.

The 2017 Nobel Peace laureate, the International Campaign to Abolish Nuclear Weapons, was also critical of Trump's decision. 

With files from Reuters and CBC News