Poland will deliver an initial batch of four Soviet-made MiG-29 fighter jets to Ukraine, Polish President Andrzej Duda said Thursday, ramping up pressure on other NATO allies to make similar commitments.

The planes are in “full working order” and will be delivered in “the next few days,” Duda said at a news conference in Warsaw alongside his Czech counterpart, Petr Pavel. The delivery would mark the first time any of Ukraine’s NATO allies have delivered jets.

“We are literally sending these MiGs to Ukraine at this moment,” he said.

Poland is in the process of upgrading its air force with South Korean-made FA-50 fighters and American-made F-35s, as it rapidly expands its military amid the war in neighboring Ukraine. It has about a dozen of the MiG-29s available that are “mostly” functional, Duda said, adding that the remainder will be “serviced and prepared” before also being donated.

Poland has played a leading role in getting taboo-breaking weaponry to Ukraine. As Germany stalled on sending tanks this year, Duda announced that Poland had decided to send them. Polish officials said it was part of a strategy to ramp up public pressure on Germany to approve the delivery of the German-made tanks.

Ukraine has been pushing hard in recent months for Western countries to donate fighter jets, with President Volodymyr Zelensky dubbing them “wings for freedom.” Poland and Slovakia, which has also said it is ready to send its Soviet-era jets to Ukraine, have called on other countries to do the same as part of an international coalition.

Ukraine already has its own MiG-29s, meaning that Ukrainian pilots will be able to fly them without additional training, Duda said.

In February, Britain announced that it would begin training Ukrainian pilots on fighter jets used by NATO. Both British Prime Minister Rishi Sunak and French President Emmanuel Macron have said they have not ruled out contributing fighter jets to Ukraine, but they suggested that nothing would be immediate.