Germany has not yet decided whether to send Leopard tanks to Ukraine, or allow other countries to donate theirs, despite pressure on Berlin to act.
A meeting on Friday to co-ordinate military donations for Kyiv did agree to supply more armoured vehicles and air defence systems.
But Ukrainian President Volodymyr Zelensky earlier made a specific appeal for modern tanks to repel Russia.
Poland’s foreign minister criticised Germany’s reluctance to send tanks.
“Arming Ukraine in order to repel the Russian aggression is not some kind of decision-making exercise. Ukrainian blood is shed for real. This is the price of hesitation over Leopard deliveries. We need action now,” Zbigniew Rau wrote on Twitter.
Western countries have committed billions in other weaponry – but without Germany’s commitment on tanks, it was not the result Ukraine was hoping for.
Ukraine wants German-made Leopard 2s as they are easy to maintain and designed specifically to compete with the Russian T-90 tanks, which are being used in the invasion.
There are believed to be more than 2,000 Leopard 2 tanks worldwide and President Zelensky believes about 300 of them would help ensure it can defeat Russia.
However, under German export laws, other countries who want to supply German-made Leopard 2s – like Poland and Finland – are unable to do so until Berlin gives the all-clear.
Ukraine already has tanks, but they are old, Soviet-era machines, prone to breaking down and without the upgraded armour and sophisticated laser range-finders found on modern Nato tanks.
The country knows its best, perhaps only, chance of fending off the massed assault Russia is expected to launch in the coming months is fielding a sizable force of western-supplied armour.
Mr Zelensky said there was “no alternative” to supplying his country with tanks in a video address on Friday evening: “Each arrangement must be carried out as quickly as possible – for our defence.”
Earlier this week, Germany was reported to have made a decision on providing the tanks – which would be done on the condition the US agreed to send its advanced M1 Abrams tank.
But speaking after Friday’s meeting of 54 countries at Ramstein air base in Germany, US Defence Secretary Lloyd Austin denied Berlin was waiting on the US to make the first move.
“This notion of unlocking – in my mind it’s not an issue,” he said.
Speaking of Germany’s wider contribution to the defence of Ukraine, Mr Austin, said: “They are a reliable ally, they’ve been that way for a very, very long time and I truly believe that they’ll continue to be a reliable ally going forward.”
He told reporters other countries were providing tanks to Ukraine: “I don’t have any announcements to make on M1s [Abrams tanks] and you heard the German minister of defence say that they’ve not made a decision on Leopards.”
Other countries have committed to sending tanks, including the UK, which will send 14 Challenger 2s. (BBC)