Washington rejected Warsaw’s proposal to transfer Polish MiG-29 fighter jets to Ukraine through a US military base in Germany as the West seeks ways to help Kyiv fight the Russian invasion but fears being sucked into a war with nuclear-armed Moscow.

Asked about the offer of Polish MiGs, the Kremlin described it as a potentially dangerous and undesirable scenario.

Ukraine has pleaded with western nations to provide it with fighter jets to counter a Russian invasion that has forced more than two million refugees to flee the country, and US lawmakers have responded by pushing President Joe Biden’s administration to facilitate the transfer of aircraft.

On Tuesday, Poland said it was ready to deploy all its MIG-29 jets to Ramstein Air Base in Germany and put them at the disposal of the US, urging other Nato members to do the same. The Pentagon later dismissed the offer as not “tenable”.

“Such a serious decision as supplying planes must be unanimous and unequivocally made by the whole North Atlantic alliance,” Polish Prime Minister Mateusz Morawiecki said during a news conference in the Austrian capital Vienna broadcast on Polish television.

“We did not agree to supply planes by ourselves, because it must be the decision of the whole of Nato,” he added.

Ukrainian President Volodymyr Zelenskiy has also repeatedly asked the West to implement a no-fly zone over Ukraine, but the US and its Nato allies have rebuffed those calls fearing a direct confrontation with Moscow.

Russia’s defence ministry has warned that countries offering air fields to Ukraine for attacks on Russia may be considered as having entered the conflict.

Polish deputy foreign minister Pawel Jablonski told public radio station Polskie Radio 1 that Poland had to prioritise its security when considering the supply of jets to Ukraine.

“It cannot be that Poland has — as the only Nato country — to take the risk, and the other countries would not have to compensate or share it with us in any way,” he said.

The MiG-29 is a fighter jet that was developed in the Soviet Union and as Ukraine’s military already flies Russian-made aircraft it is the best choice for Ukrainian pilots who already know how to operate them, experts say. Combat pilot training on US-made aircraft can take years and requires a different pipeline for maintenance.

Moscow has targeted Ukrainian cities, sending some 2 million civilians fleeing and triggering more EU sanctions on Russian banks and trade, as well as blacklisting of officials and oligarchs.

Poland is the largest ex-communist state in Nato and the EU, and has a long history of fighting Russia and seeking to integrate with the West. It now sits on the eastern border of both blocs.