Poland has officially asked Germany for permission to export a host of Leopard 2 battle tanks to Ukraine in a move which raises pressure on Berlin to make a decision on the thorny issue.
The German government told the BBC it had received the request to export 14 German-made tanks on Tuesday.
But it has insisted the final decision lies with Chancellor Olaf Scholz.
Ukraine sees the tanks as vital for breaking through Russian lines and to beat an anticipated counter offensive.
The Leopard 2 tanks were specifically designed to compete with the Russian T-90 tanks, which are being used in the invasion. But export laws mean any country that wishes to send the tanks require Berlin's permission.
Poland's prime minister Masteusz Morawiecki said he hoped Germany would quickly respond to the request, and accused Germany of "delaying, dodging, acting in a way that is difficult to understand".
He also said Poland would ask the European Union to compensate the cost of the tanks it wants to send to Ukraine.
Germany has been hesitant to send the vehicles, or allow other nations to do the same, with one of its concerns being the fear that a sudden move on the issue could further escalate the conflict with Russia.
On Tuesday Germany's Defence Minister Boris Pistorious said Berlin had given allied nations the green light to train Ukrainians to use Leopard 2 tanks, but did not commit to sending their own.
Mr Pistorious said a decision about supplying the tanks would be made soon. The military's Chief of Staff added that any decision would be tacked at a political level.
"We are encouraging our partners if they want to, and if they have the opportunity, to start training Ukrainian forces on these Leopard vehicles," Mr Pistorious said in a news conference with Nato secretary general Jens Stoltenberg.
Allied nations have become frustrated at what they perceive as German reluctance to send the armoured vehicles in recent days.
Speaking on Tuesday, Poland's Defence Minister Mariusz Blaszczak said he was appealing to Germany to "join the coalition of countries supporting Ukraine with Leopard 2 tanks".
"This is our common cause, because the security of the whole of Europe is at stake!" he added.
On Tuesday Lithuanian president Gitanas Nauseda said he believed Poland was determined to send their tanks to support Ukraine after meeting with the Polish president Andrezej Duda.
"It is a pity that at sometimes there is a completely unnecessary delay as we could have made decisions sooner. The Polish side is very keen to provide such support," Mr Nauseda said.
But Mr Pistorious defended German chancellor Olaf Scholz against criticism that he was dragging his feet on sending the vehicles to Kyiv.
"Taking the lead does not mean blindly going ahead," he said. "And if the decision takes another day or two, then that's just the way it is."