A coalition of 11 nations will start training Ukrainian pilots to fly F-16 fighter jets in Denmark in August, while a training center will also be set up in Romania, officials said on the sidelines of a summit of NATO leaders in the Lithuanian capital Vilnius. 

"Hopefully we will be able to see results in the beginning of next year," Denmark's acting defense minister Troels Lund Poulsen said.

NATO members Denmark and the Netherlands have been leading efforts by an international coalition to train pilots and support staff, maintain aircraft and ultimately supply F-16s to Ukraine.

So far, no countries have committed to sending F-16s to Ukraine, though Poland and Slovakia have supplied 27 MiG-29s to supplement Ukraine's fleet of combat aircraft.