The US government has approved the delivery of F-16 fighter jets from Denmark and the Netherlands to Ukraine’s air force to defend against Russia as soon as Ukrainian pilots are trained, a US official said Thursday.

Kiev has been asking its Western allies to supply it with F-16s to counter Russian air superiority since last year.

Washington has given assurances to Copenhagen and Amsterdam that it will fast-track all requests for transfers of the Lockheed Martin-built fighters so that Kiev can acquire F-16s once Ukrainian pilot training is completed.

The Danish and Dutch governments have recently asked for guarantees on this. They are the two countries that have taken the lead in pilot training for the Ukrainian Air Force.

US Secretary of State Anthony Blinken has sent letters to his Danish and Dutch counterparts to assure them that approvals will be granted, according to the US official.

“I am writing to express the full support of the US for both the deliveries of fighters to Ukraine and the training of Ukrainian pilots by certified instructors,” Mr Blinken said in the letters, seen by Reuters.

“It remains critical that Ukraine is able to defend itself against Russia’s continued aggression and violation of its national sovereignty,” the US Secretary of State added.

He explained that approving deliveries from third countries would allow the Ukrainian armed forces to “fully utilize the new capabilities once the training of their first group of pilots” is complete.

The US president approved the training of Ukrainian pilots in the F-16 in May. However, no clear timetable has been given for the deliveries.