The US has rejected Poland’s offer to send MiG-29 fighter jets to Ukraine via a US airbase in Germany, citing “serious concerns” for the entire NATO alliance.

Warsaw made the unexpected offer on Tuesday, despite Ukraine’s President Volodymyr Zelenskyy’s repeated requests for more warplanes to replenish his country’s air force as it defends against invading Russian forces.

The Polish plan called for Russian-made MiG-29 fighter jets to be delivered to a US base in Ramstein, Germany, before being deployed to Ukraine.

However, Pentagon spokesman John Kirby stated that the possibility of the jets flying from a US-NATO base “into contested airspace with Russia over Ukraine raises serious concerns for the entire NATO alliance.”

“We will continue to consult with Poland and our other NATO allies about this issue and the difficult logistical challenges it presents,” Kirby said in a statement.

“It’s just not clear to us that there’s a substantive reason for it,” he added.

While a significant portion of Ukraine’s air force has remained intact since the conflict began on February 24, both Ukraine and Russia have suffered significant losses, and neither controls the country’s airspace.

Ukraine’s air force fleet consists of Soviet-era MiG-29 and Sukhoi-27 jets, as well as heavier Sukhoi-25 jets – and these are the only planes Ukrainian pilots can fly right away without additional training.

While Ukraine has increased calls for Western allies to supply it with military jets, providing Kyiv with warplanes poses significant risks.

Russia has warned that supporting Ukraine’s air force will be interpreted in Moscow as participation in the conflict, potentially subjecting suppliers to retaliation.

NATO has stated that it does not want direct conflict with Moscow, a fellow nuclear-armed power, and US President Joe Biden has stated that sending American troops into Ukraine to fight is not an option, which the Pentagon has stated would apply to troops on the ground or in the air, flying missions.

Following Poland’s announcement, US Undersecretary of State for Political Affairs Victoria Nuland told US lawmakers that Washington had been caught off guard.

“To my knowledge, it wasn’t pre-consulted with us that they planned to give these planes to us,” Nuland told a Senate Foreign Relations Committee hearing. “So I think that actually was a surprise move by the Poles,” she said.