WASHINGTON -- The United States is planning to reimpose sanctions on Iran, said US Treasury Secretary Steven Mnuchin on Thursday, ahead of President Donald Trump's decision on whether to extend sanctions relief on Iran under the 2015 nuclear deal.

"I am expecting new sanctions on Iran. We continue to look at them. We've rolled them out," Mnuchin told reporters at a White House briefing Thursday afternoon.

Mnuchin's remarks came as the world is waiting for Trump to decide if he will reimpose sanctions on Iran, a move that may endanger the landmark Iran nuclear deal.

Trump's decision was expected to be made at a "decision meeting" on Thursday, said US State Department spokesperson Stephen Goldstein.

"I'm not sure when the announcement will be, whether it will be tonight, or whether it will be tomorrow. But we do expect a decision to be made later today," Goldstein told reporters during a Thursday afternoon briefing.

In a telephone conversation with Trump on Thursday, French President Emmanuel Macron reiterated "the determination of France to support the strict implementation of the 2015 Iran nuclear agreement and the importance of it being respected by all signatories," said the Elysee Palace.

In July 2015, after a decade of strenuous negotiations, Iran and six major countries, namely, China, Russia, Britain, France, the United States and Germany, struck a final agreement on Iran's controversial nuclear program, in which the West promises to relieve sanctions on Tehran in exchange for a halt in Iran's efforts to develop a nuclear weapon.

However, as one of the most significant diplomatic legacies of Trump's predecessor Barack Obama, the hard-won nuclear deal formally known as the Joint Comprehensive Plan of Action (JCPOA) has been running the gauntlet of Trump on his campaign trail and since he became president.

In October, Trump announced that he had decided to decertify Iran's compliance with the pact.

His move triggered a 60-day window for Congress to decide whether to reimpose sanctions on Iran. Reimposing sanctions would mean violating the Iran nuclear deal on the US side.

The Congress did not come up with any resolution, thus passing the ball back to Trump, who should decide on Friday if he would like to waive energy sanctions on Iran.

Despite the Iran nuclear deal, the United States has kept on slapping separate sanctions on Iran, accusing the country of having a ballistic missiles program as well as human rights abuses.