Iran has said it will withdraw from at least part of the 2015 nuclear accord known as the Joint Comprehensive Plan of Action (JCPOA) if the other – in particular European – countries still party to the agreement are unable to provide relief from re-imposed US sanctions.

Specifically, the Iranian government has threatened to resume higher enrichment of uranium within 60 days if the other signees fail to negotiate new terms for the deal that US president Donald Trump gave notice of quitting a year ago.

As the saber rattling continued, with the US sending an aircraft carrier and a bomber wing to the Persian Gulf, European governments as well as Russia and China warned both sides not to escalate the conflict.

US secretary of state Mike Pompeo, said US action will depend on “what Iran does, not what it says it may do.”

While the UK and the US agree on the need to confront the threat of Iran recommencing higher enrichment of uranium, British Foreign Secretary Jeremy Hunt said it is "no secret” that the two sides “have a different approach on how best to achieve that."

Hunt urged Iran to uphold the 2015 deal, asserting simltaneously that "as long as Iran keeps its commitments, so will we.”

German foreign minister Heiko Maas said his government has learned of Iran's announcement with “great concern,” while insisting that “all steps must be avoided that could endanger regional stability and security."

Maas said Berlin also wants to hold onto the nuclear deal.

Also voicing “deep concerns” about Iran’s proposed partial withdrawal from the JPCOA, France's defense minister Florence Parly said the “question of sanctions will be raised" if the nuclear deal isn't respected.

Did US withdrawal provoke Iranian threat?

Outside Europe, many commentators – led by Russian foreign minister Serge Lavrov – said the US had provoked Iran’s non-compliance threat by announcing in April that it would end six-month waivers from sanctions for countries still buying oil from the OPEC country in May.

After a meeting with Iranian counterpart Javad Zarif in Moscow, Lavrov said the US is making it difficult for Iran to fulfill its obligations as well as for the general state of the nuclear non-proliferation regime.

At the meeting, Zarif said Iran's decision to partially withdraw from certain provisions of the accord does not violate it.

Even as he called on all parties concerned to “exercise restraint,” a Chinese Foreign ministry official said China appreciates Iran's "strict implementation" of its 2015 nuclear deal, despite the US withdrawal.

Countries found to breach US sanctions could themselves face sanctions for engaging with Iran, a situation that led to EU companies such as French energy and petrochemicals group Total and German chemical giant BASF to abandon plans to resume business in the country that were floated after the JPCOA signing.

Total’s envisioned projects in Iran were the most ambitious. For fear of being excluded from the much larger US market, the French group has said it will not be able to stick with preliminary agreements to build ethane-fed petrochemical and polymerisation plants worth some $2 billion.