DAVOS: Ukrainian President Volodymyr Zelensky urged his Western allies to take quicker decisions to help his war-struck country on Wednesday, warning that "tyranny is outpacing democracies".

In an address to the World Economic Forum in Davos by videolink, the Ukrainian leader issued a "call for speed" in a barely veiled reference to hesitations in Germany about whether to supply heavy Leopard tanks to the country.

"The time the Free World uses to think is used by the terrorist state to kill," Zelensky said ahead of a meeting of Ukraine's Western arms suppliers in Germany on Friday.

"The world must not hesitate today or ever," he added. "The mobilisation of the world must outpace the next military mobilisation of our joint enemy."

Zelensky says Russian 'terror' can only be stopped on the battlefield

Leaders and ministers from Finland, Lithuania, Poland and Britain have added their voices in recent days to a growing clamour for Berlin to approve the export of German-made Leopards to Ukraine.

Polish President Andrzej Duda, whose country has offered to send its Leopards, called it a "very, very, very good idea" on Tuesday.

Ukraine's backers are set to meet at the US-run Ramstein military base in Germany on Friday.

"I hope it will be very positive for Ukraine. Unofficially, I have very good and positive signals," Kyiv mayor Vitali Klitschko told AFP on Wednesday.