The buck-passing between Poland and the US over the possible use of elderly MiG-29s to hit Russian forces inside Ukraine is one of the west’s few diplomatic failures of the past month. It also raises questions about how far European countries are prepared to escalate militarily before they believe they will touch a dangerous Russian tripwire.

The US and Europe have worked hard to keep their differences over sanctions and oil embargos to a public minimum, and tried to accommodate each other’s national interests. So it was striking on Tuesday when first the Pentagon described a Polish offer to send planes to the US airbase in Ramstein as “untenable”, and then the deputy US secretary of state said the US had not been consulted about the plan.

Part of the problem was that the Polish proposal was subtly but critically different to a scheme that had previously been discussed in private. Against the backdrop of highly charged diplomatic tensions, presentation matters.

In essence, Poland said it would cooperate in strengthening the Ukrainian air force so long as this would be seen in Moscow as a US, Nato or EU scheme but not a Polish one.

In its original, US-conceived iteration, the proposal was a trilateral deal whereby Poland would hand over the MiGs to Ukrainian pilots to fly into their homeland, and the US would then provide some substitute planes. Boris Johnson, an enthusiast, described the plan as “rent a MiG”.

That proposal, arguably, was not qualitatively different to Nato members providing Ukraine with Javelin anti-tank missiles. In return, Poland would eventually fill the hole in its air force with 28 F-16s being provided by the US.

But under private pressure from the US, Poland felt the plan unduly exposed its citizens to Putin’s ire. So instead, in a game of diplomatic pass the parcel, Poland tweaked the proposals so the planes would be sent free of charge to the US airbase in Ramstein, Germany, rather than being flown out of Poland into Ukraine. The move would literally take Poland out of the line of Russia’s fire since the plan could be labelled as that of the US, Nato or the EU.

Poland also suggested other frontline Nato countries with MiG planes should match its plan, a proposal directed at Slovakia and Romania. If executed it would mean Ukraine had 70 extra planes at its disposal.

The Pentagon’s response – “it is simply not clear to us that there is a tangible justification for this” – was swift. Passing the parcel back, it said any decision to hand over planes ultimately rested with the Polish government, although it did not kill off the proposal altogether.

It is possible that Poland’s nationalist government launched its plan with the aim of relieving pressure from the US Congress and the Ukrainian president, Volodymyr Zelenskiy, knowing full well it would be rejected.

Either way the public spat is a setback. Over the weekend the US secretary of state, Antony Blinken, had said a plan involving planes was under active consideration.

The upshot after this mini-debacle is Russia retains air superiority. Ukrainian pilots who were being trained in Poland to fly the planes are now grounded with no machines with which to defend their country. An opportunity has been squandered.

The episode may have lessons for both sides. The possibility of making the MiG-29s available first appeared publicly on 27 February, when the EU made the unprecedented decision to provide military aid to a country outside the bloc. The first tranche of equipment for Ukraine is expected to amount to €500m (£417m), but up to €5bn is to be spent under the European Peace Initiative.

It was then that the head of EU diplomacy, Josep Borrell, said that aid for Kyiv would also include offensive weapons, including planes. At that point it became clear that the planes would only be MIG-29 and Su-25, because Ukrainian pilots only have experience with these machines. Poland, it would seem, did not appreciate the issue being disclosed.

However, the country has emerged strengthened in another way from the past 24 hours. The US has provided Poland with two Patriot defence missiles. Each battery consists of two firing platoons with two launchers. This means there will be 16 launchers in Poland. They can have either four or six missiles. The latest Pac-3 MSE missiles are capable of shooting down the Russian Iskander ballistic and manoeuvring missiles.

Unfortunately, they are also the anti-aircraft defence that Ukraine lacks. Nato, as its constitution requires, looks after its own.