Bloomberg | Hussein Ibish: The State Department won�t get far by arguing the U.S. remains a participant in the nuclear deal.

The Trump administration is attempting to have it both ways over the Iranian nuclear deal. In an effort to extend an international arms embargo on the Islamic Republic beyond its scheduled expiration in October, the State Department is preparing to claim that the U.S. remains a �participant state� in the Joint Comprehensive Plan of Action that Iran agreed with the world powers in 2015.

It has been nearly two years since President Donald Trump withdrew the U.S. from that deal, and started to impose harsh economic sanctions�periodically intensified�on the Islamic Republic. This has proved an effective tool to pressure other countries not to do business with Iran, even though United Nations-approved international sanctions on Iran were nominally eased when it signed the JCPOA.

But now the administration is worried that if the arms embargo is allowed to end, the terms of the deal would allow the regime in Tehran to purchase advanced weapons systems, such as fighter jets and tanks. The State Department is hoping to forestall that that eventuality by threatening to using the JCPOA to reinstate binding international sanctions within 65 days.

How would that work? First, the U.S. would have to invoke terms of the JCPOA that allow any other signatory to activate the dispute-resolution process if it believes Iran has violated the agreement. Iran has exceeded limits on stockpiling enriched uranium, among several other breaches.

A joint commission would then have 15 days for deliberations. If Washington isn�t satisfied�and it won�t be�the matter would be referred to the signatory foreign ministers for another 15 days of discussion. Presuming the Trump administration remains unmoved, the joint commission would then have five more days to hear from an advisory board.

The process would then shift to the UN Security Council, where Washington�s unilateral power would kick in. The council must pass a resolution to continue sanctions relief for Iran. Without such a resolution, the pre-JCPOA restrictions�including the arms embargo�would automatically snap back into effect. An American veto would ensure the resolution does not pass.

That, at any rate, is the theory. But the State Department hasn�t explained how the U.S. will justify invoking the terms of the JCPOA after Trump rejected the agreement. The European signatories�Germany, France and Britain�are unlikely to buy the claim that the U.S. remains a party to the deal. Russia and China definitely won�t. If the other parties won�t recognize the U.S. right to begin the dispute-resolution process and the joint commission never meets, the gambit would quickly fail.

For its part, Iran will see any effort to block arms purchases as grounds for additional provocations.

But the arms embargo isn�t the only objective here. A faction within the administration led by Secretary of State Mike Pompeo and National Security Advisor Robert O�Brien believes that, with U.S. sanctions having crippled Iran, now is the time to pile on more pressure and compel Tehran to come to new terms.

Trump�s sanctions have indeed damaged Iran�s economy, which is now receiving a further battering from the coronavirus crisis and the collapse in oil prices. In geopolitical terms, the Islamic Republic is under significant pressure in regional hotspots like Syria and Iraq.

The Iranians have responded with a string of provocations�including missile attacks by surrogate Iraqi militias against the U.S. military in Iraq and naval confrontations in international waters�that simultaneously indicate desperation and, arguably, justify yet more American pressure.

The Trump administration insists that its broader goal is to compel Iran to negotiate a better nuclear deal that also addresses Tehran�s missile program and its support for sectarian militia groups in neighboring Arab countries.

That�s a vital goal. So too is extending the arms embargo: An Islamic Republic with advanced weapons systems would be a far greater threat to its neighbors and to the wider world.

Effective and sustained pressure on Iran could help secure both objectives. The embargo, even if extended on paper, won�t be effective if Russia and China decide to sell weapons to Iran anyway. A serious diplomatic effort is required to convince them not to. This would need European support, not exasperation over at attempted legal workaround.

By trying to have its cake and eat it too, the Trump administration will only succeed in further alienating allies and damaging the global standing of the U.S.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.