Poland announced Tuesday that it would hand over all of its MiG-29 fighter aeroplanes to the United States, potentially furthering an agreement that would allow the fighters to be passed on to Ukraine’s military as it battles invading Russian forces.

The Pentagon rejected Poland’s proposal to transfer MiG-29 fighter jets to the US for delivery to Ukraine, calling it not “tenable,” according to Pentagon press secretary John Kirby on Tuesday.

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Ukraine has been clamouring for more jets, and Washington is considering a proposal in which Poland would supply Ukraine with Soviet-era fighters in exchange for American F-16s to compensate for the loss. Ukrainian pilots are trained to operate fighter jets from the Soviet era.

In a statement, the Polish Foreign Ministry stated that Poland was ready to give the jets to the US Ramstein Air Base in Germany promptly and free of charge.

“At the same time, Poland requests the United States to provide us with used aircraft with corresponding operational capabilities,” it said.

The Polish government also urged other MIG-29 jet owners to follow likewise.

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Bulgaria and Slovakia, both former Soviet-bloc NATO members, still have Soviet-made fighter jets in their air forces.

The handover of Poland’s 28 Soviet-made MiG-29 fighter jets would symbolise the West’s determination to do more to deter Russia. It is unlikely to be a game changer militarily. The number of planes is relatively low. The MiG-29s are also inferior versus more advanced Russian aircraft, making them easy prey for Russian pilots and missiles.

Russia has warned that assisting Ukraine’s air force may be interpreted in Moscow as participation in the conflict, potentially subjecting providers to reprisal.

It would also weaken Poland’s own air force at a time when Eastern Europe is under attack.

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The transfer of the MiGs to Ukraine is laden with issues because neither NATO nor the European Union want to be regarded as directly involved in the deal, which will exacerbate already high relations with Russia. The US has no intention of transferring the planes directly to Ukraine.

To keep the appearance that NATO and the EU are not directly involved in the Ukraine crisis, US and Polish officials have been discussing a number of solutions. The first step is Poland’s “donation” of MiGs to the US, which Poland announced on Tuesday.

According to one scenario, Poland would transport the fighter jets to a US facility in Germany, where they would be repainted and flown to a non-NATO, non-EU country. Under that suggestion, Ukrainian pilots would come to fly them to Ukraine.

Although no country has been formally designated as a transit site, Kosovo, a non-aligned country with close ties to the US, has been considered as one of several nations that would be ready to act as a middleman.

Poland had requested that the United States supply it with F-16 fighter jets to replace the MiGs.

However, F-16 production is backlogged, and the next recipient in line for new deliveries is Taiwan, which is facing increasing Chinese threats and has strong bipartisan support in Congress.

The Polish government expressly requested “used” planes in its statement, a distinction that would allow the Biden administration to avoid legislative resistance to making Taiwan wait for its F-16s.

Earlier Tuesday, British Defense Secretary Ben Wallace said his country would stand with Poland if it gave over the jets, warning that the decision might have a “direct consequence.”

“And so we would protect Poland, we’ll help them with anything that they need,” Wallace said on Sky News.

According to Polish Prime Minister Mateusz Morawiecki, any decision regarding the delivery of offensive weapons must be made unanimously by NATO countries.

“This is why we are able to give all of our fleet of jet fighters to Ramstein, but we are not ready to make any moves on our own because … we are not a party to this war,” he said.