By taking a couple of small, carefully calibrated steps towards the exit from the 2015 nuclear deal, Iran has given Europe and China a two-month ultimatum to stand up to the US on the world stage, or risk a slide towards a new Middle East conflict.

The erosion of that multilateral agreement and the return to military posturing in the Persian Gulf, has been driven by a small number of radical players in the Trump administration, the Israeli government, and the Saudi and Emirati monarchies. In the US and Israel, this has happened in the face of resistance from the defence establishment.

In the year since Donald Trump abrogated the multilateral agreement with Iran – by which Tehran accepted stringent limits on its nuclear programme in return for sanctions relief – the European, Russian and Chinese parties to the deal swore to uphold it. But they have failed so far to shield Iran from redoubled US sanctions.

Q&A What is the Iran nuclear deal? Show In July 2015, Iran and a six-nation negotiating group reached a landmark agreement known as the Joint Comprehensive Plan of Action that ended a 12-year deadlock over Tehran’s nuclear programme. The deal, struck in Vienna after nearly two years of intensive talks, limited the Iranian programme, to reassure the rest of the world that it cannot develop nuclear weapons, in return for sanctions relief.

At its core, the JCPOA is a straightforward bargain: Iran’s acceptance of strict limits on its nuclear programme in return for an escape from the sanctions that grew up around its economy over a decade prior to the accord. Under the deal, Iran unplugged two-thirds of its centrifuges, shipped out 98% of its enriched uranium and filled its plutonium production reactor with concrete. Tehran also accepted extensive monitoring by the International Atomic Energy Agency (IAEA), which has verified 10 times since the agreement, and as recently as February, that Tehran has complied with its terms. In return, all nuclear-related sanctions were lifted in January 2016, reconnecting Iran to global markets. The six major powers involved in the nuclear talks with Iran were in a group known as the P5+1: the UN security council’s five permanent members – China, France, Russia, the UK and the US – and Germany. The nuclear deal is also enshrined in a UN security council resolution that incorporated it into international law. The 15 members of the council at the time unanimously endorsed the agreement. On 8 May 2018, US president Donald Trump pulled his country out of the deal. Iran announced its partial withdrawal from the nuclear deal a year later. Saeed Kamali Dehghan, Iran correspondent

Corporations feared being blacklisted in the US more than they feared losing a share in the Iranian market. European efforts to insulate its companies from sanctions have so far proved flimsy.

Tehran’s initial response to Trump’s effort to destroy the deal was strategic patience, relying on the rest of the world to keep its economy afloat.

Iran hoped that Beijing at least would defy the US and continue to buy its oil when the US ended sanctions exemptions for the last handful of Iran’s remaining customers on 2 May. So far, that has not happened. Now, Beijing is nervous about derailing delicate trade talks with Washington, and Chinese imports have dipped.

Russia has voiced support for Iran – but is not an oil customer and carries little weight in the global economy.

“For the Europeans, the Chinese and Russians, the nuclear deal has been a priority but it has not been in the top three priorities. It has been the sacrificial lamb,” said Ellie Geranmayeh, senior policy fellow at the European Council on Foreign Relations.

By raising the stakes, Iran has challenged Europe and China to wean themselves off dependence on the dollar – for both a long-term aspiration. Iran is now giving them 60 days to take significant strides or face a potentially severe new crisis in the Middle East.

The initial two steps announced by President Hassan Rouhani are at the very low end of the scale of available measures. Iran will stop exporting low enriched uranium (LEU) and heavy water – a trade which had kept its stockpiles of both under the levels set by the 2015 deal.

For the time being, these steps will have a negligible impact on the central purpose of the agreement: keeping Iran at least a year away from the capability to make a nuclear warhead.

The actual LEU stockpile had settled below the agreed 660lb limit and heavy water has no immediate use, as Iran currently has no functioning heavy water reactor or reprocessing plant necessary to make plutonium.

The US announced last week that it would begin sanctioning trade in both materials making it harder for the Iran to keep to the agreed limits. By limiting its initial steps to these two measures, Tehran has insured that the blame resides almost entirely in Washington.

Much more serious are the steps Iran is threatening to take after the 60-day deadline. Rouhani has it will lift the agreed 3.67% limit on the level of purity to which it enriches uranium. For every percentage point that figure is allowed to creep up, Iran gets exponentially closer to the capacity to produce weapons-grade uranium.

Rouhani said that if the ultimatum is not met, Iran will also end a Chinese-led initiative to redesign its heavy water reactor in Arak. If that happened, the route to producing plutonium would be open once more.

Such steps, which could bring Iran’s breakout time to below a year, would almost certainly trigger the reimposition of UN and EU sanctions, and an accelerated round of escalation. Iran has even threatened to leave the Non-Proliferation Treaty (NPT), signalling an intention to make nuclear weapons.

An NPT withdrawal, or any Iranian move to hinder the oil trade passing through the Strait of Hormuz – another Iranian threat – would bring a military confrontation significantly closer.

It is now China and Europe’s move. As a huge oil importer and party to the 2015 deal, Beijing is uniquely placed to demonstrate the agreement’s benefits to the Iranian people.

Germany, the UK and France have launched a euro-based payment system, known as Instex, intended to insulate Iranian transactions from US sanctions. It is expected to accommodate non-oil transactions, including food and humanitarian aid, but it has taken a long time to establish and is not yet online.

Although accelerating work on Instex would not do much for Iran’s economy in real terms, it would be a sign of political will to defy Trump and uphold the deal.

“The Europeans thought they would be appease Trump and ease the ‘maximum pressure’ policy on Iran. Clearly that is not working out,” said Dina Esfandiary, an Iran expert at the Belfer Centre for Science and International Affairs at Harvard University.

Meanwhile, China is rethinking its policy, Esfandiary added. “For them it will be a trade-off between highlighting their economic and political sovereignty or safeguarding trade with the US and economic growth.”