"There is not a particular weapon system that is a silver bullet. A balance of all systems is needed," said US General Christopher Cavoli, Supreme Allied Commander in Europe, after a meeting of NATO military chiefs.

But he added that "it's clearly the case that modern Western technology is outperforming Russian technology" on the battlefield in Ukraine.

The comments came as pressure mounted on Germany from Kyiv and some NATO allies to send Leopard II battle tanks to help Kyiv push back Moscow's forces.

The head of NATO's military committee, Admiral Rob Bauer, steered clear of calling for the equipment to be sent to Kyiv but said that "if the Russians are fighting with tanks, the Ukrainians need tanks as well".

He said having tanks was important for the Ukrainians to both match the Russians and "in terms of their ambition to regain their own territory".

Bauer said Russia was likely planning a new offensive in spring as Moscow had not changed its overall objective of defeating Ukraine.

"That's what the Ukrainians have to prepare for. That's what they are thinking about," he said.

He said that assistance from NATO allies was being shaped by this "to see what the Ukrainians most likely need most and then how the allies can support".