Volodymyr Zelenskyy said on Tuesday that he had received a “serious and solid” offer from the leaders of countries that are ready to supply Kyiv with F-16 fighter jets, and he is waiting for final agreements with Ukraine’s allies, Reuters reports.

“Our partners know how many planes we need,” Zelenskyi said, according to a message on the Ukrainian president’s website.

“We have already received estimates of the number (of aircraft) from some of our European partners… This is a serious and solid proposal,” he said.

“Kyiv is now waiting for a final agreement with its allies, including a ‘joint agreement with the United States,'” Zelenskyi also noted. It is still unclear which of Kyiv’s allies is ready to send planes to Ukraine.

Last month, US President Joe Biden told G7 leaders that Washington supports joint training programs for allies for Ukrainian F-16 pilots. But US national security adviser Jake Sullivan said there was no final decision on whether Washington would send the planes.

Zelensky has long called for F-16s, saying that their use by Ukrainian pilots would be a sure signal to the world that the Russian invasion would end in defeat.

Russia said on Tuesday that US-built F-16 fighter jets could “host” nuclear weapons and warned that giving them to Kiev would further escalate the conflict.