Germany said Monday that customs issues are holding up its plans to set up a repair and maintenance site in Slovakia for weapons used by Ukraine to repel Russian troops.

"At the moment, we still have customs aspects that have to be sorted out," a German defence ministry spokesman said. 

"We would like things that come in for repair to flow back to Ukraine more quickly... That is not the case at the moment," he added.

Berlin is working on "alternative solutions", he said, declining to provide further details on these possibilities.

Germany has supplied Ukraine with military gear ranging from rocket launchers and an air defence system to howitzers.

It recently also agreed to send Leopard battle tanks much sought by Kyiv.

But beyond deliveries of new gear, the country is now racing to set up facilities closer to Ukraine where the supplied equipment can be maintained and repaired.

Slovakia's geographical position next to Ukraine has made it a choice location for such a facility.