Two senior Trump administration officials told Reuters on Wednesday that the president, a Republican, had privately expressed reluctance to heed the advice of top advisers recommending he not reimpose the suspended sanctions.
In October of last year, Trump refused to recertify that Iran was in compliance with the agreement, saying the it was "one of the worst and most one-sided transactions the US has ever entered into". "It's going to be complicated to save the deal after this", said one European diplomat, speaking on condition of anonymity.
Washington also imposed sanctions on the head of Iran's judiciary and others.
Iran's Foreign Minister Mohammad Javad Zarif said earlier on Twitter that the deal was "not renegotiable" and that Trump's move "amounts to desperate attempts to undermine a solid multilateral agreement".
Under its terms, economic sanctions against Iran were to be lifted in exchange for Tehran halting uranium enrichment.
Under the deal, the U.S. president must sign a waiver suspending the U.S. sanctions on Iran every 120 days. The Treasury Department's action hits 14 Iranian officials and companies and businessmen from Iran, China and Malaysia, freezing any assets they have in the U.S. and banning Americans from doing business with them.
European countries including France and Italy have benefited from renewed trade with Iran, whose proven natural gas reserves are as vast as Russia's, while Britain reopened its embassy in Tehran following the deal.
Trump plans to negotiate a separate agreement to address flaws he says exists in the Joint Comprehensive Plan of Action (JCPOA), the official name for the 2015 agreement. His ouster in a U.S-backed coup in 1953 led to the return to power of the exiled shah of Iran. Iran must allow "immediate inspections at all sites requested by international inspectors", he said, and "sunset" provisions imposing limits on Iran's nuclear program must not expire.