Trashing it as "the worst deal ever", US President Donald Trump declared the official withdrawal of the United States from the Iran nuclear deal on May 8, 2018.

But while praising his prescient boss' foresight "that the Iran deal was a crazy, bad deal", US State Secretary Mike Pompeo now wants the world to believe his country remains a participant in the deal.

It takes extraordinary concentration to keep abreast of the US administration's policy flip-flops, so frequent are they. But given the previous bombastic rhetoric, this one is even harder than usual for the rest of the world to digest.

If the claim has been made for the utilitarian purpose of tightening the screw on the Islamic republic, there is little chance it will succeed.

The 2015 deal, officially known as the Joint Comprehensive Plan of Action, was reached between Iran and six key stakeholders, including the US. It offers Iran relief from international sanctions in exchange for restraints on its nuclear pursuits.

Hailing it as culmination of diplomatic efforts for "a comprehensive, long-term and proper solution" to the Iran nuclear issue, the UN Security Council unanimously adopted Resolution 2231 (2015) endorsing the hard-earned deal.

If it was blind confidence in its "maximum pressure" that led the US administration to leave the deal two years ago, it is the tacit, belated awareness of the invalidity of such a tactic that has prompted its latest about-face and is driving its present attempt to sustain the UN resolution, which expires in October.

Claiming it is still a legal party to the deal because it is named in the UN resolution, the US is threatening to trigger a so-called snapback of all UN sanctions on Iran, including the arms embargo, using a process outlined in the nuclear deal, if the resolution is not extended.

Then comes Washington's self-made dilemma: how can it claim the right to act from within a deal after officially consigning it to the trash can? After their high-profile departure from the table, how can Pompeo and his colleagues convince the rest of the world they are still there?

It looks equally challenging for Washington to prove either Teheran's alleged "significant nonperformance", or its own presence in the deal.

Having made such a song and dance about not wanting to be party to the deal, the US is unlikely to find much support for that claim. Nor should it, since it cannot just shuffle in and out of multilateral agreements based on whether it thinks they can be molded to its purpose at any particular point in time.