KHARKIV, Jan 10 (AFP) - Ukrainian Foreign Minister Dmytro Kuleba on Tuesday (Jan 10) said Germany's refusal to send his country battle tanks was costing lives as Berlin's top diplomat vowed further support during a surprise visit.

German Foreign Minister Annalena Baerbock's unannounced trip came just days after Chancellor Olaf Scholz agreed to provide to Ukraine Marder infantry fighting vehicles long sought by Kyiv in its battle against Russia's invasion.

But Berlin has so far declined to supply Ukraine with more advanced Leopard battle tanks. Kuleba, accompanying Baerbock during her visit to the eastern city of Kharkiv, pressed Germany again to send them.

The "longer it takes to make the decision, the more people will die", he said.

"I have no doubt that Ukraine will receive German Leopard tanks. I think the German government somewhere deep down understands that this decision will be made and the tanks will be transferred to Ukraine."

Baerbock, who on Tuesday became the highest-level Western official to visit Kharkiv, pledged further German support for Kyiv.

"In all parts of Ukraine, from Kharkiv to Kherson to Kyiv, people should know they can rely on our solidarity and support," she said.

She stressed that Germany will keep supplying weapons "that Ukraine needs in order to free its citizens who are still suffering under the terror of Russian occupation".

Baerbock brought with her a "further help package" of power generators, €20 million (US$21 million) for demining and €20 million as financial help for the Starlink project ensuring internet access for the population.

Baerbock's visit was kept secret for security reasons and announced only as she made her way back to Berlin.

She said she wanted to get a picture of the situation on the ground and send her message of solidarity to Ukrainians.