German Defence Minister Boris Pistorius, on a surprise visit to Kyiv, said between 20 and 25 of the tanks would arrive by summer, about 80 by the end of the year and another 100 in 2024, according to a statement by Ukrainian Defence Minister Oleksii Reznikov's office after the counterparts met.

In Washington, Robert Habeck, Germany's vice chancellor, said that while Ukraine should have a double-digit number of German-made Leopard 1 tanks at its disposal in the first quarter, it was unclear how many of the 178 tanks his country had authorized would ultimately be sent.

"The numbers are there but they have to be refurbished for battle, re-equipped, so we don't know exactly how many," he told reporters after meeting U.S. Secretary of State Anthony Blinken and National Security Adviser Jake Sullivan. "But it's a large number to repel Russia's spring offensive."

Asked whether the decision to send them, after months of mounting pressure on Berlin, should have been taken earlier, Habeck said: "I hope the decision was taken at just the right time."

The joint statement about the plans by Denmark, Germany and The Netherlands said Ukraine would receive at least 100 of the Leopard 1 A5 tanks in coming months as well as training, logistical support, spare parts and an ammunition package.

Dutch Defence Minister Kasja Ollongren said the Leopard 1 was "definitely still suitable" for combat use despite being an older model.

"It's really a tested tank," she said on Dutch national broadcaster NOS. "They're being fixed up and made battle-ready, so they will definitely be useful for the Ukrainians, and also better than a number of Russian tanks."

Details of the deal still need to be worked out with the companies that own the tanks, according to the statement.

It was also not immediately clear whether there would be cost-sharing with the companies. There are some 180 Leopard 1 tanks in Germany owned by arms maker Rheinmetall (RHMG.DE) and a company in northern Germany.

Standing beside Reznikov in Kyiv, Pistorius noted he had earlier seen off Ukrainian forces departing for training in Germany on the more modern Leopard 2 tanks his country has also promised Ukraine.

Reznikov tweeted a picture of himself and Pistorius posing with a scale model Leopard in a display case, writing: "The 'first' Leopard 2 has arrived in Kyiv." The German defence ministry later tweeted that the actual Leopard 2s would be available at the end of March.

Denmark, Germany and the Netherlands said their Leopard 1 initiative was open to further partners, adding Belgium had shown "initial interest to participate".

Earlier, the head of German arms maker Rheinmetall said it would send Ukraine 20-25 Leopards this year, with the rest of the 88 Leopard 1 tanks it owns in total to be sent next year.

The move follows the German government's decision last month, amid mounting international pressure, to deliver more modern Leopard 2 battle tanks from army stocks.