Spain will send six of its German-made Leopard tanks to bolster Ukraine's fight against Russia, Defence Minister Margarita Robles said Wednesday.

The six tanks are currently being repaired and Madrid could send more Leopards to Ukraine "if it is necessary" and if "our allies ask for it", she added in parliament.

"We are working in full coordination with our allies," she said, without specifying when the tanks would be sent.

Robles had said last month that Spain was ready to send some of its Leopard tanks to Ukraine, without saying how many.

The announcement that Spain would send six of its tanks comes after German Chancellor Olaf Scholz said Friday that allies with available battle tanks should send them now.

Scholz's call marked a dramatic reversal of roles, having initially resisted pressure from allies to authorise the delivery of German-made Leopard tanks to Ukraine.

Germany relented in January, saying it would itself send a company of 14 Leopard 2 A6 tanks, with the aim of assembling along with allies two tank battalions for Ukraine.

But NATO partners are struggling to make up the numbers for a full battalion of the more modern tanks.

A recent analysis by the International Institute for Strategic Studies (IISS) concluded that if Kyiv was to receive about 100 such tanks, the effect could be "significant".