The US has declared economic war on Iran: after having pulled out of the UN security council-endorsed nuclear deal in May, the Trump administration is now unilaterally combating the right of the rest of the world to engage in legal trade with the Islamic Republic.

This policy is based on the claim that Iran is a major security threat to the American people. But that is transparently exaggerated. And the statement by Mike Pompeo that sanctions will be used to ensure Iran “behaves like a normal country” is unintentionally ironic.

The US is not a “normal” country. Complicity in a horrifying aggression against Yemen and supporting the extension of Israeli colonisation of Palestine are not acts of normality. The truth is that all who intervene in the Middle East’s regional struggles, including Iran, are doing what states always have done – trying to influence outcomes in the direction of their real or perceived interests.

Nevertheless, the US has determined that its stance towards Iran should be a belligerent one. Will that reap any strategic rewards?

As UK ambassador to Tehran in 2005, I received the country’s rejection of the first attempt by the west to strike a nuclear deal, alongside my French and German colleagues. Analysts often go wrong because we think that the fights to come will be like the fights of our day, but this is what I believe may happen.

In my view, Iran will remain basically stable despite the surge in inflation and tough recession that the IMF says are coming down the line. Discontent, and maybe protests, will significantly increase. Iran’s leaders will nevertheless try to weather the storm. The 2020 US election will be crucial for them. They could not live with a four-year extension of the crisis if Trump were to win again. Their aim will be to hunker down until then. I expect them to refrain in the meantime from provoking the US in the region or reopening closed-down parts of their nuclear infrastructure.

Ayatollah Khamenei is uncompromising. Indeed, all of Iran’s leaders are resolute. The economic damage and popular suffering over the next two years is unlikely to be sufficient to make the government move. And, crucially, there is no internationally agreed campaign against Iran this time. The EU, for example, has designed a work-around to achieve some financial flows, though the Iranians are not relying on this ever working.

For his part, Donald Trump has indicated he wants a North Korea-type breakthrough. He says that Iran is changing. Among leading US politicians, calls are growing for negotiations to deliver a supposedly better replacement deal.

But this seems improbable. Iran is open to negotiations, but only on terms that it deems acceptable. Like the US, it will try to build a position of strength from which to talk. The bottom line is that Iran will only change tack when it thinks it can expect genuine American concessions.

And all the while there are risks for the US if it does not lower its sights. Chinese, Indian and Turkish demand for Iranian oil could prompt the creation of alternative channels of exchange in world trade, leading to a fall in the standing of the dollar and of the ability of the US to weaponise it in future.

There is also a risk of war by miscalculation. Or even by intention: the US could respond to the failure of its policy by upping the ante and starting a war, with the support of some countries in the region. That said, Trump does appear to want to avoid another war of choice in the region, and launching one would not be good for his re-election chances.

Only a shift in approach, namely the dropping of many of the demands for changes in behaviour, showing a modicum of respect, and opening negotiations on realistic terms, will work. Provided Iran can be made to believe that – this time – sanctions relief will be real, it should be possible to win Iranian concessions on missiles’ range and type. An eventual successor nuclear deal and some regional pullback in conjunction with peace settlements across the Middle East is possible.

Should the US be prepared to move away from diktat to an incremental approach, the UK could work with France and Germany to reassemble the security council-based coalition that negotiated with Iran from 2013.

With its current policies, however, rather than reaping strategic rewards, the US may be putting on a show of weakness to the world. With no prospect of bringing allies to its side or forcing Iran to accept its excessive demands, it is on a hiding to nothing.

• Richard Dalton is a former British ambassador to Iran