President Donald Trump will unveil a more aggressive strategy to check Iran's growing power Friday, but stop short of withdrawing from a landmark nuclear deal or declaring the powerful Islamic Revolutionary Guard Corps a terrorist organization.

During a speech at 12:45 pm (1645 GMT) from the Diplomatic Reception Room of the White House, Trump will declare the 2015 agreement -- which curbed Iran's nuclear program in return for sanctions relief -- is no longer in the US national interest.

Trump will withdraw presidential support for the landmark nuclear deal -- known as the JCPOA -- but will stop short of killing the agreement, his Secretary of State Rex Tillerson said.

"The intent is that we will stay in the JCPOA, but the president is going to decertify."

"We're saying, fine, they're meeting the technical compliance," he said indicating that the broader agreement would remain intact for now.

That will leave US lawmakers to decide its fate.

Trump had repeatedly pledged to overturn one of his predecessor Barack Obama's crowning foreign policy achievements, deriding it as "the worst deal" and one agreed to out of "weakness."

The agreement was signed between Iran and six world powers -- Britain, China, France, Germany, Russia and the US -- at talks coordinated by the European Union.

It stalled Iran's nuclear program and marginally thawed relations between Iran and what Tehran dubs the "Great Satan."

But opponents, and even some supporters, say it also prevented efforts to challenge Iranian influence across the Middle East.

In his speech, Trump will rail against Iran's "destabilizing influence" in the Middle East, "particularly its support for terrorism and militants," according to a fact sheet released by the White House.

"We don't think that nuclear agreement should define the entire policy," said Tillerson. "There are also many more immediate concerns we have with Iran's destabilizing activities in the area and in the region."

Tillerson cited the threat to US and allies' interests from Iran's proxy forces, ballistic missile development and eventual nuclear ambitions.

Trump has railed against the deal since he was a presidential candidate, and told aides earlier this year he will not recertify it.

But since coming to office, he has faced intense lobbying from international allies and his own national security team, who argued it should remain in place.

Both the US government and UN nuclear inspectors say Iran is meeting the technical requirements of its side of the bargain, dramatically curtailing its nuclear program in exchange for sanctions relief.

In another partial climbdown, Trump is also expected to levy limited sanctions against the Revolutionary Guards, rather than invite retaliation by designating it as a terrorist organization.

Apart from running swaths of Iran's economy and Iran's ballistic program, the corps is also accused of guiding bellicose proxies from Hezbollah in Lebanon, to the Huthi in Yemen to Shiite militia in Iraq and Syria.

"We have considered that there are particular risks and complexities to designating an entire army, so to speak, of a country," Tillerson said.

Instead the US will squeeze those directly supporting the corps' "terrorist activities, whether it's weapons exports or it's weapons components, or cyber activity, or it's movement of weapons and fighters around."

- Snap back -

Still, Trump's tough-guy approach could yet risk undoing years of careful diplomacy and increasing Middle East tensions.

Iranian President Hassan Rouhani lashed out at his US counterpart saying he was opposing "the whole world" by trying to abandon the landmark nuclear agreement.

"It will be absolutely clear which is the lawless government. It will be clear which country is respected by the nations of the world and global public opinion," he added.

Congress must now decide whether to end the nuclear accord by "snapping back" sanctions, which Iran demanded be lifted in exchange for limiting uranium enrichment.

Trump will not ask Congress to do that, Tillerson said. "A re-imposition of the sanctions," he said, "would, in effect, say we're walking away from the deal."

But lawmakers may yet decide torpedo the agreement.

Proposals by Republican Senators Tom Cotton and Bob Corker to introduce "trigger points" for new sanctions and extend sanctions beyond a pre-agreed deadline have spooked allies, who believe it could breach the accord.

But it remains unclear if their proposals can garner the 60 votes need to pass the Senate.

- Allies pleading -

Right up until the last minute, the other signatories to the deal have urged Washington not to let it fall apart.

"We believe this deal is important to ensuring the international nuclear nonproliferation regime and regional peace and stability. We hope all parties can continue to preserve and implement this deal," Chinese foreign ministry spokeswoman Hua Chunying said.

The Kremlin warned that ditching the agreement could "unequivocally damage the atmosphere of predictability, security, stability and non-proliferation in the entire world."

Tillerson spent much of the week on the telephone, talking through a decision that is deeply unpopular with allies.

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.

Source: AFP