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The Trump administration is weighing whether to effectively break the terms of a landmark 2015 Iran nuclear deal, Secretary of State Rex Tillerson said late Tuesday.

While campaigning for president, Donald Trump repeatedly called the agreement "the worst deal ever negotiated." Contradictory statements as to whether Trump would scrap it entirely or simply vigilantly enforce it raised questions about how he would proceed once in office.

Tillerson notified Congress that despite finding that Iran is in compliance with the agreement, the White House is looking at whether the U.S. should break with the deal because of Iran's continued support of terrorism.

In a letter to House Speaker Paul Ryan, the secretary of state said that "Iran remains a leading state sponsor of terror through many platforms and methods."

The six powers that negotiated the deal which went into effect in January 2016 — the U.S., China, Russia, France, Germany and the United Kingdom, with involvement from the European Union — set aside Iran's alleged support for terrorism in order to get a deal guaranteeing that Iran would not be able to build a nuclear weapon for a decade and would remain under the eye of U.N. inspectors.

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Although billions of dollars of Iran's assets were unfrozen as a result of the negotiations, U.S. sanctions against Iran because of their support of terrorism were not considered to be part of the agreement.

The certification of Iran's compliance, which must be sent to Congress every 90 days, is the first issued by the Trump administration. The deadline for the certification was midnight.

The review specifically looks at whether sanctions relief granted Iran through the deal is in the U.S. national interest. Trump would work with Congress once the inter-agency review is complete, Tillerson said.

At the time the deal was reached, Trump called the Iran deal "terrible" and said it would "lead to nuclear Holocaust."

Israeli Prime Minister Benjamin Netanyahu has criticized the deal. He said in July of 2015 that "Iran is going to receive a sure path to nuclear weapons."

Former president Obama has said the deal will make the world safer and more secure.

"Iran will not get its hands on a nuclear bomb," he said in January of 2016 after the deal was implemented.

At the time, Obama said that Iran's current uranium stockpile is 2 percent of what it was before the agreement, and the country has removed two-thirds of its centrifuges.

After the International Atomic Energy Agency verified in January of 2016 that Iran was in compliance with terms to scale back its nuclear program, some international sanctions were lifted.

The sanctions drastically reduced crude oil exports from Iran. Since the sanctions have been lifted, oil exports from Iran to India have surged, Reuters reported in February.

Iran was exempted from an OPEC deal to reduce output by 1.2 million barrels per day starting Jan. 1, a victory for Tehran which argued it needs to regain the market share it lost during sanctions.