Berlin said late last month that it was aiming to send around 30 battle tanks to help Ukrainian forces fight Russia's invasion after pressure from Kyiv and its supporters to greenlight the supplies.

But German Defence Minister Boris Pistorius said after a meeting of Ukraine's backers in Brussels that so far it had gathered only 14 newer A6 type Leopard tanks and three from Portugal.

"Let's be clear: we have not reached a battalion," Pistorius said.

"It will be half a battalion."

He added: "For the German Leopards, I want to say again that ours will be delivered in the last week of March. That is certain."

Germany, Poland and Ukraine held talks with other NATO members on the sidelines of a meeting in Brussels on Tuesday to try to whip up more tanks for Kyiv.

Pistorius said more talks would take place with potential donors later this week.

He said Berlin was against the Netherlands sending 14 Leopard 2 tanks as that would "weaken the operational readiness" of a joint German-Dutch brigade where they are used.

Ukraine has pleaded with its Western backers to send modern battle tanks to help it push back a renewed Russian offensive and allow it to go on the attack itself.

Poland has also committed to sending a battalion of Leopard 2 tanks to Kyiv and is currently training Ukrainian troops to use them.

Canada has already sent several Leopard tanks and Norway has pledged eight more.