By Stephanie van den Berg

EINDHOVEN, Netherlands (Reuters) -The Netherlands and Denmark have said they will definitely give F-16 fighter jets to Ukraine once conditions for the transfer have been met, Dutch Prime Minister Mark Rutte said on Sunday as Ukraine's President Volodymyr Zelenskiy visited his country.

Rutte said that the Netherlands has 42 F-16s available in all, but it is too early to say whether all of them will be donated.

"Today we can announce that the Netherlands and Denmark commit to the transfer of F-16 Aircraft to Ukraine and the Ukrainian Air Force, including cooperation with the United States and other partners once the conditions for such a transfer have been met," he said in a joint press conference with Zelenskiy at a military air base in Eindhoven.

Zelenskiy who called the deal a "breakthrough agreement" said the exact number of aircraft will be discussed "a little later".

The pledge is the first real promise of F-16's for Ukraine's armed forces and comes a few days after the United States approved the possible delivery of the fighter jets by the Netherlands and Denmark.

Zelenskiy arrived in the Netherlands on Sunday as part of an ongoing push to boost Ukraine's air defences, and is expected to continue to Denmark later in the day. The Danish Foreign ministry also confirmed its commitment to delivering F-16s in a statement on Sunday.

The Netherlands, together with Denmark, has in recent months led international efforts to train Ukrainian pilots for F-16's and to ultimately deliver the jets to help counter the air superiority of Russia, whose forces invaded Ukraine in February 2022.

"The main issue is F-16 for Ukraine to protect our people from Russian terror. We are getting stronger", Zelenskiy said in a post on Telegram earlier on Sunday.

Ukraine's Defence Minister Oleksiy Reznikov on Saturday said training had begun for Ukrainians to operate F-16's, but added it would take at least six months and possibly longer to also train engineers and mechanics.

Training will take place in Denmark and Romania, officials from a coalition of 11 nations have said.

Ukraine, which expects several dozens of pilots to be trained, said last week it did not expect to be able to use F-16's this autumn or winter.

The Netherlands can deliver F-16's as its armed forces are transitioning to newer F-35 fighters.

On Saturday Zelenskiy was in Sweden, where he discussed the possibility of receiving Gripen jets.

(Reporting by Bart Meijer and Toby Sterling in Amsterdam, Stephanie van den Berg and Piroschka van der Wouw in Eindhoven, Jacob Gronholt-Pedersen in Copenhagen and Pavel Polityuk in Kyiv; Editing by David Goodman, Elaine Hardcastle)