USinfo-icon President Donald Trump is expected to refuse to certify Iraninfo-icon's compliance with the landmark 2015 nuclear deal, an agreement between worldinfo-icon powers and Tehraninfo-icon aimed at limiting the latter's nuclear programme to non-military purposes.

The move comes despite thinly-veiled criticisms from US allies in Europe who have developed burgeoning commercial and political ties with Iran. Trump is to lay out his plan in a 16:45 GMT speech at the White House on Friday.

Trump's withdrawal of endorsement would mean US lawmakers could vote to introduce new sanctions against Iran, which Iranian leaders say could lead to their country's partial or complete withdrawal from the deal.

The agreement was signed between Iran and six world powers -- Britain, Chinainfo-icon, Franceinfo-icon, Germany, Russiainfo-icon and the US -- at talks coordinated by the European Unioninfo-icon.UN nuclear inspectors say Iran is meeting the technical requirements of its side of the bargain, dramatically curtailing its nuclear programme in exchange for sanctions relief.So, while US officials still insist that "America First" does not mean "America Alone," on this issue they are starkly isolated. The other signatories all back the deal.

"This is the worst deal. We got nothing," Trump thundered to Fox News on Wednesday. "We did it out of weakness when actually, we have great strength." Trump, whose address to this year's UN General Assembly was a hymn to national sovereignty, has been railing against the Iran deal since before he was elected.

In the office, he has chafed at being required under US law to re-certify Iran's compliance with the accord every 90 days, declaring that Tehran has broken it "in spirit." Now, as he prepares to roll out a broader US strategy to combat Iran's expanding power in the Middle East, he feels the time has come to turn his back on the deal.

Right up until the last minute, America's closest allies have urged Trump to think again.

After his nationalist UN speech, EU foreign policyinfo-icon chief Federica Mogherini warned that the deal "doesn't belong to one country... it belongs to the international community." US allies have not been convinced by the argument that the deal fell short because it left Iran free to develop ballistic missiles and sponsor proxy militias in its region.

"Mixing everything means risking everything," a French diplomatic source said. "The existential threat is the bomb. The nuclear deal is not meant to solve Lebanoninfo-icon's problems." Europe fears not only that Iran will resume the quest for the bomb but that the US is relinquishing its leadership role in a stable, rules-based international system. 

What is JCPOA? 

Often abbreviated to "the Iran deal" or "Iran nuclear deal", JCPOA is an agreement between Iran and the five permanent members of the UN Security Council plus Germanyand the EU to ensure its nuclear programme is limited to civilian use.

The deal, which was signed in October 2015 and implemented at the start of 2016, followed years of negotiation between the US, represented by then-Secretary of State John Kerry, and Iran, represented by Foreign Minister Mohammad Javad Zarif. 

The agreement requires Iran to completely eliminate stockpiles of medium-enriched uranium and drastically reduce reserves of low-enriched uranium. 

The material in its high-enriched form is required to produce nuclear weaponsinfo-icon. Iran denies that it has ever had the aim of producing a nuclear weapon. Iran also agreed to reduce the number of centrifuges capable of enriching uranium.

In return, UN sanctions related to Iran's nuclear programme were lifted, as were some EU sanctions.

The US ended some secondary sanctions against non-US businesses and individuals who engaged in commercial activity with Iran. Frozen Iranian assets, valued at over $100bn, were also released back to Tehran.