Last October, Trump decertified to Congress Iran's compliance with the pact, regardless of reports provided by the International Atomic Energy Agency, the international non-proliferation watchdog, confirming that Tehran has been in full compliance with the deal.
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Still, Mr Trump's expected action is most important for what he will not do: reinstate sanctions on Iran's central bank and oil exports, which were lifted in return for constraining its nuclear programme.
Q&A Why is Trump hostile to Iran?
The United States meant to work with its European partners on a follow-on agreement which enshrines certain "triggers" that Iran can not exceed related to ballistic missiles and inspections, said senior Trump administration officials on Friday while briefing reporters about Trump's decision.
While approving the waiver on USA sanctions related to the nuclear deal, Washington announced other sanctions against 14 Iranian entities and people, including judiciary head Ayatollah Sadeq Larijani, a close ally of Iran's Supreme Leader Ayatollah Ali Khamenei. As a result, a geopolitical crisis has been postponed, but not avoided.
What does Mr Trump want to change?
America's allies see the accord as the best way of thwarting Iran's quest for nuclear arms and a victory for multilateral diplomacy.
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While there may be some relief that Trump has yet to torpedo the hard-won accord, there were clear signs of frustration from European capitals in the runup to the decision. They have yet to figure out how to work constructively with him, to shape the sort of world order that is to his tastes.
President Donald Trump is expected this week to extend relief from economic sanctions to Iran as part of the nuclear deal, citing progress in amending U.S. legislation that governs Washington's participation in the controversial accord, according to USA officials and others familiar with the administration's deliberations.
However, Trump, who has previously vowed to scrap the nuclear pact, was privately expressing reluctance to heed the advisers, the officials said. Instead of developing Iranian society, Khamenei and his henchmen steal the people's wealth and national treasure and use both to line their pockets and pay for their wars overseas.
"One of the things that should be noted, and it's often overlooked, is that the sanctions that were imposed on Iran's ballistic missile programs are still in place", he says.
Trump has argued that his predecessor, President Barack Obama, a Democrat, negotiated a bad deal for the United States in agreeing to the nuclear accord. The pressure from allies has been unusually public.
Many of those sanctions - including one targeted at Larijani - were in response to the Iranian government's crackdown on peaceful protests that have swept the country in recent weeks.
The foreign ministers of Britain, Germany, France as well as Iran's Mohammad Javad Zarif, are expected to meet on Thursday morning with Mogherini, the EU's foreign policy chief.
Germany, France, Britain and the European Union are "fully aware that Iran's continued compliance [is] conditioned on full compliance by the US", Iranian Foreign Minister Mohammad Javad Zarif warned on Twitter following talks in Brussels with his German, French and British counterparts, as well as European Union foreign policy chief Federica Mogherini. Late previous year, in equally striking comments, the German ambassador to Washington warned that tearing up the nuclear deal when Iran is abiding by its requirements risked sending a unsafe message to North Korea, should a nuclear pact with that country become possible.