Ukraine expected its military efforts to be boosted by the arrival of F-16 aircraft promised by allies this summer, but so far Ukraine has not yet seen them, Ukrainian President Volodymyr Zelenskyy said.

"It's been 18 months and the planes have not reached us," he said in an interview with the BBC, adding that he is grateful for what has already been provided to Ukraine.

Zelenskyy stressed that new fighters are needed to help Ukrainians eliminate Russian air dominance and unblock the skies.

Zelenskyy previously said that Ukraine needs at least 128 F-16 fighters to create effective competition for Russia in the skies.