With the deadlocked war in Iran about to enter its fourth month, loose comparisons with previous US quagmires in Iraq, Afghanistan and Vietnam are bandied about. When the conflict began, warnings of another “forever war” seemed exaggerated. No longer. As matters stand, the negative international humanitarian, economic and geopolitical fallout from this fiasco looks set to prove more permanently globally damaging than any of those past US-made disasters.

That being the case, an urgent question arises, not least today as reports suggest the US president and his secretary of war are planning to rain more bombs on Iran: who will stop Donald Trump?

Having started something he cannot finish, the US president, egged on by Israel’s warmonger-in-chief, Benjamin Netanyahu, has boxed himself into a corner. Either he resumes the illegal bombing of Iran on an even bigger scale, brazenly threatening war crimes in hopes of forcing surrender; or else he accepts a negotiated compromise that falls embarrassingly short of his initial aims, including eliminating Iran’s nuclear programme, and leaves an angry, more hardline, strategically strengthened regime in power.

Neither choice is attractive – or tenable – for Trump. He and his fanatical sidekick, Pete Hegseth, should know by now that bombing cannot blow away Iran’s defiance and resilience. It is not even militarily effective: 70% of Iran’s missile stockpile reportedly remains intact. In any case, Trump’s threats to break the ceasefire, like his aborted Project Freedom in the strait of Hormuz, are opposed by Gulf states fearful of more retaliatory attacks, by Washington’s allies, Israel excepted – and by most US voters.

A peace deal, with add-ons, that is broadly in line with Barack Obama’s 2015 nuclear pact with Tehran, which Trump foolishly wrecked and is now the most Iran seems willing to offer, would rightly be counted an abject Trump failure. It would represent a landmark US strategic defeat with significant implications for the global contest with China and Russia. And any deal that left the regime charging transit fees in the strait of Hormuz would be utterly humiliating. No amount of spin could conceal such a presidency-defining calamity.

Trump knows he cannot simply do nothing. Lurching indecisively back and forth, he appears both manic and Micawberish. Blood-curdling threats are followed, often in the same day, by claims that something will turn up. In one sense, that’s his problem. The collapse in his approval ratings to about 37% is fully deserved. Unfortunately, the standoff is also doing immense, possibly irreversible harm to people all across the world. Trump’s Iran problem is everyone’s problem now.

So the question must be asked again: who will stop Trump?

Among the poorest countries, the need to end the war is not ideological. It’s existential. Staples such as rice and wheat have doubled in price in Somalia since the conflict began. Shortages of fertiliser could ruin the growing season, presaging devastating famines. The World Food Programme predicts that, if the war continues, an additional 45 million people will face acute hunger. And the misery is exacerbated by Trump’s and the UK’s (and other countries’) foreign aid cuts.

The economic impact on the better-off is painfully evident, too. Developed countries from Europe to Asia are penalised through spiralling energy, fuel, food and commodity prices, the full impact of which has yet to be felt. Last month, the IMF cut its global growth forecast to 3.1% in 2026, blaming the “shadow of war”. In effect, ordinary people everywhere are paying a Trump war tax.

Trump’s war is upending the geopolitical balance. The US is now publicly at odds with its closest allies, Germany, France and Britain. The Gulf states, too, are questioning a US alliance that has made them Iranian targets. All this is boosting Russia, whose oil exports face reduced sanctions, and hurting Ukraine. Meanwhile, to the consternation of Japan, South Korea, the Philippines and Taiwan, this month’s Beijing summit confirmed China’s growing global ascendancy as a subservient, clueless Trump failed to secure its help on Iran.

The universally negative knock-on effects of this unprovoked, avoidable conflict unfold daily. It undermines democratic accountability, political stability, human rights, the UN charter, the Geneva conventions, environmental conservation and climate policy, common decency and, most of all, common sense. Yet where is the furious shout of global outrage at what Trump, almost single-handedly, is doing to the world? Where is the pushback as this crisis intensifies?

An ever-expanding catastrophe is not inevitable. Trump must and can be stopped.

Radical, concerted action is urgently required. Western governments wield most leverage, individually and collectively. If Britain, for example, truly has a “special relationship” with the US, now is the time to exploit it for the general good. Emmanuel Macron, France’s president, has urged so-called “middle powers” such as Canada, India, Brazil and Japan to join Europe in a “coalition of independence”. Now is the time to deploy this idea in the battle to make Trump see reason.

Where governments are already grouped together, as in the EU, the African Union, the G20 and Brics, a much tougher, united approach to Washington is necessary. If Trump continues to block meaningful peace talks, the US should face a downgrading of ties, punitive sanctions and import tariffs. Next month’s EU summit, and the G7 summit in France that precedes it (which Trump is expected to attend), is the moment when leaders of other western democracies, acting together, must finally bring him to heel.

The UN security council is another platform where greater pressure should be applied. What if France and the UK were to join China, Russia and other members in demanding an immediate, permanent end to hostilities, followed by independent mediation? That may give Washington pause. European Nato members could suspend or limit non-Ukraine military cooperation. More US bases in Europe could face restrictions or closure. And why maintain the fiction of cordial diplomatic relations? Send Trump’s typically underqualified, loud-mouthed ambassadors back home for a rethink. Boycott next month’s World Cup or move matches to non-US venues. Ban McDonald’s. Ban Budweiser.

All this and more might be attempted by a global community of nations that is being seriously damaged by a capricious US war of choice and refuses to be its helpless victim. Yet the most direct way of stopping Trump remains pressure from Americans themselves. Most deplore his war. Most are enduring steep cost of living rises. They, too, worry where his tyrannical behaviour is leading. Action to stop this constitutionally unauthorised war is under way in Congress. These efforts must be redoubled. And when November’s midterm elections arrive, Trump and his spineless Republican enablers must be punished severely.

The disease of Trump and Trumpism, so destructive of the US itself, risks becoming a global pandemic. His Iran war is but a symptom. Cuba may be next to be infected. Trump must be made to understand his deficit-funded, ill-led, school-bombing, over-sized military does not make him boss of the world. A bold, radical and imaginative collective intervention by the US’s friends is urgently required. By all legitimate means, Trump must be stopped.

• Simon Tisdall is a Guardian foreign affairs commentator