US President Donald Trump is set to decide whether or not to reimpose wide-ranging sanctions on Iran, the latest action that puts into question the survival of the 2015 nuclear agreement between world powers and the Islamic Republic.

Trump, who has repeatedly vowed to "rip up" the deal signed by his predecessor Barack Obama, is expected to announce his decision to renew the waiver on US sanctions against Iran as early as Friday.

Analysts said Trump's "persistent unpredictability" has already cast a cloud of doubt over world capitals, warning that his actions could force Tehran to abandon the deal in the long run and return to all-out hostilities with Washington, DC.

As part of the implementation of the nuclear deal in 2015, US sanctions against Iran were waived. But the US president is required to renew that waiver every 120 days.

If Trump fails to do so, several US sanctions on Iran are automatically reimposed, including those against Iranian businesses and foreign companies that deal with Iran. The last time Trump issued a waiver was in September 2017, and the renewal is due on Friday.

The waiver renewal is separate from the certification of the nuclear deal every 90 days, which was imposed by the US Congress on the president. In October 2017, Trump refused to recertify that Iran was in compliance with the agreement. While the US certification process is not part of the nuclear deal, Trump's decision sparked outrage in Iran and other countries supporting it

On Thursday, ahead of Trump's decision on the sanctions, European foreign ministers met Javad Zarif, Iran's foreign minister, in Brussels to reiterate their support for the nuclear deal, warning a decision to reimpose sanctions could scuttle the landmark agreement altogether.

"The deal is working. It is delivering on its main goal, which is keeping the Iranian nuclear programme in check and under close surveillance," Federica Mogherini, the European Union's foreign affairs representative, said as she stood sternly next to her counterparts from France, Germany, and the United Kingdom.

"The unity of the international community is essential to preserve a deal that is working, that is making the world safer, and that is preventing a potential nuclear arms race in the region," she said.

"We expect all parties to continue to fully implement this agreement," Mogherini added without mentioning the United States.

For his part, Zarif posted on social media, "Any move that undermines JCPOA is unacceptable", using the acronym for the official name of the nuclear deal, Joint Comprehensive Plan of Action.

"Iranian people have every right to all its [nuclear deal's] dividends," he wrote.

'No better alternative'

Boris Johnson, foreign secretary of the UK, the closest ally of the US, also said no country "has come up with a better idea" in place of the agreement.

"I don't think that anybody has so far produced a better alternative to the JCPOA as a way of preventing the Iranians from going ahead with the acquisition of military nuclear capability," he said.

But he also said the nuclear deal should also benefit the Iranian people, who in recent weeks have come out in droves to protest against the government.

On Tuesday, Ali Akbar Salehi, Iran's nuclear chief, was quoted as telling Yukiya Amano, head of the UN nuclear watchdog, that his country is unlikely to continue cooperating with the international community if the deal falls apart.

Ellie Geranmayeh, senior policy fellow at the European Council on Foreign Relations, said there is an expectation in Europe that Trump will stay with the deal and renew the sanctions waiver.

"There is by no means certainty on that point, given what we have seen of President Trump, particularly the way he makes last-minute decisions on this issue of the nuclear deal," she said.

Geranmayeh added there is also concern the US administration and particularly the president "will be heavily influenced by the recent protests in Iran".

European foreign ministers on Thursday insisted discussions on human rights and the deadly protests across Iran should be separate from the nuclear agreement.

'Narrative of war'

Hamed Mousavi, a University of Tehran professor, said it is likely the US could impose new non-nuclear related sanctions against Iran while appearing to stay with the nuclear deal.

In that case, it will only hurt the people economically who have been protesting against the government in recent weeks, Mousavi told Al Jazeera.

"If the Trump administration continues to do that, I think it will lead down to a path that maybe Iran will withdraw in the long run because the benefits that Iran was supposed to receive out of the deal ... have been very slim," he said.

Rouzbeh Parsi, an Iran expert and senior lecturer at Lund University in Sweden, said the latest Trump move could be just another step to justify a military confrontation with Iran.

"If the unilateral withdrawal of the US seriously undermines the Iranian ability to trade with the world, it will weaken the Iranian government considerably and put it under pressure domestically to also leave the JCPOA," Parsi told Al Jazeera.

"At that point, the hawks in the US will argue that Iran’s nuclear programme is no longer curtailed and, therefore, poses an imminent threat, and so the narrative of war can be spun - yet again," he warned.

Under the 2015 deal signed in Vienna by the US, Russia, Germany, France, Britain, China, and the EU, Iran scaled back its uranium enrichment programme. According to nine reports by UN nuclear inspectors, Iran has continued to be in compliance with that condition.

In exchange, sanctions on Iran's economy were lifted, and Tehran was allowed to resume trading oil and gas on the international market. A total of $100bn in frozen Iranian assets was also released. Since then, Iran has gradually opened its country to foreign investment and welcomed more foreign visitors, injecting billions of dollars into its ailing economy.

But since Trump took office in January 2017, a cloud of uncertainty has returned on Iran with his repeated statements calling the deal an "embarrassment" and the "worst deal" the US ever entered into.