"The Iran Deal was one of the worst and most one-sided transactions the United States has ever entered into," he said.

He even called the deal as "decaying and rotten".

He said: "The Iran Deal is defective at its core. If we do nothing, we know what will happen. In just a short time, the world’s leading state sponsor of terror will be on the cusp of acquiring the world’s most dangerous weapons."

Trump said: "At the heart of the Iran deal was a giant fiction: that a murderous regime desired only a peaceful nuclear energy program. Today, we have definitive proof that this Iranian promise was a lie."

Trump said his government is going to reimpose economic sanctions that were waived when the deal was signed in 2015.

A White House statement on the issue said: "President Donald J. Trump is terminating the United States’ participation in the Joint Comprehensive Plan of Action (JCPOA) with Iran and re-imposing sanctions lifted under the deal."

President Trump is terminating United States participation in the JCPOA, as it failed to protect America’s national security interests, read the statement.

The President has directed his Administration to immediately begin the process of re-imposing sanctions related to the JCPOA.

The White House statement said the re-imposed sanctions will target critical sectors of Iran’s economy, such as its energy, petrochemical, and financial sectors. 

"United States withdrawal from the JCPOA will pressure the Iranian regime to alter its course of malign activities and ensure that Iranian bad acts are no longer rewarded.  As a result, both Iran and its regional proxies will be put on notice.  As importantly, this step will help ensure global funds stop flowing towards illicit terrorist and nuclear activities," read the statement.

Iran, in response, has said that it is preparing to restart the process of uranium enrichment.

Iran's President Hassan Rouhani was quoted as saying by BBC: "I have ordered the Atomic Energy Organisation of Iran to be ready for action if needed, so that if necessary we can resume our enrichment on an industrial level without any limitations."

World Reacts

French President Emmanuel Macron said France, Germany, and the UK regret the U.S. decision to leave the JCPOA.

"France, Germany, and the UK regret the U.S. decision to leave the JCPOA. The nuclear non-proliferation regime is at stake," Macron tweeted.

European Union diplomatic chief Federica Mogherini regretted Trump and his administration's decision on nuclear deal.

"The European Union regrets today's statement by the President of the United States on the nuclear deal with Iran [Joint Comprehensive Plan of Action, JCPOA]. Should the US reconsider this position, we would welcome it," she said in a statement.

"The United States remain our closest partner and friend, and we will continue to work together on many other issues. As we have always said, the nuclear deal is not a bilateral agreement and it is not in the hands of any single country to terminate it unilaterally," she said.

Israeli Prime Minister Benjamin Netanyahu, however, welcomed the  US action and Donald Trump's 'bold decision' and tweeted: "Israel fully supports @realDonaldTrump’s bold decision today to reject the disastrous nuclear deal with the terrorist regime in Tehran. The deal didn’t push war further away; it actually brought it closer. The deal didn’t reduce Iran’s aggression; it dramatically increased it."

Following a decision on Tuesday by the United States to withdraw from the 2015 nuclear agreement with Iran, the United Nations chief said he was “deeply concerned” by the move, and called on all parties to preserve the deal.

In a statement released shortly afterwards, UN Secretary-General António Guterres said: “I am deeply concerned by today’s announcement that the United States will be withdrawing from the Joint Comprehensive Plan of Action (JCPOA) and will begin reinstating US sanctions.”

“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 added.

“It is essential that all concerns regarding the implementation of the Plan be addressed through the mechanisms established in the JCPOA,” Mr. Guterres stressed, adding that “issues not directly related to the JCPOA” should be addressed separately.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.

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