US defence secretary Lloyd Austin meets new German defence minister a day before allies meet to discuss military aid.

Ukraine has upped its call for the West to finally sendheavy tanksas the defence chiefs of the United States and Germany headed for a showdown over weapons Kyiv says could decide the fate of the war.

US defence secretary Lloyd Austin is in Germany on Thursday, meeting its new defence minister a day before they host a meeting of dozens of allies to pledge weapons for Ukraine.

Fridays meeting, at the US Ramstein air base in Germany, has been billed as a chance to provide the arms to shift the wars momentum in 2023.

Top of the agenda is heavy tanks, which Kyiv says it needs to fend off a new Russian onslaught and launch counter-offensives to recapture its occupied territory.

Austin and Boris Pistorius, Germanys new defence minister, talked in Berlin just hours after Pistorius was sworn into office on Thursday.

But there was no word on whether they had resolved differences that could see Berlin block Western plans to send Kyiv heavy tanks when dozens of allies gather at Ramstein, Washingtons main European air base.

We have no time, the world does not have this time, Andriy Yermak, head of the Ukrainian presidential administration, wrote on the Telegram messaging app on Thursday.

The question of tanks for Ukraine must be closed as soon as possible, he said.

We are paying for the slowness with the lives of our Ukrainian people. It shouldnt be like that.

A Leopard 2 tank is pictured during a demonstration event held for the media by the German Bundeswehr in Munster near Hannover, Germany, September 28, 2011 [Michael Sohn, AP Photo]

Ukrainian President Volodymyr Zelenskyy made a similar plea by video link to leaders gathered at the World Economic Forum in Davos on Wednesday, urging them to supply his country before Russia mounts its next missile and armoured ground attacks.

The supplies of Western tanks must outpace another invasion of Russian tanks, Zelenskyy said.

But for the West to send tanks, Washington will have to resolve a standoff with Berlin, which has so far demurred from authorising countries to send its Leopard 2 tanks, the workhorse of militaries across Europe.

Washington and many Western allies say the Leopards which Germany made in the thousands during the Cold War and exported to its allies are the only suitable option available in big enough numbers.

A German government source said Berlin would lift its objections if Washington sends its own Abrams tanks.

But US officials say the Abrams is inappropriate for Ukraine because it runs on turbine engines that use too much fuel for Kyivs strained logistics system to keep them supplied at the front.

Poland and Finland have already said they would send Leopards if Germany lifts its veto, and other countries have indicated they are ready to do so as well.

Britain added to the pressure by breaking the taboo on heavy tanks last week, offering a squadron from its fleet of Challengers, though far fewer of these are available than Leopards.

Colin Kahl, the Pentagons top policy adviser, said on Wednesday Abrams tanks were not likely to be included in Washingtons next $2bn military aid package, which will include Stryker armoured vehicles.

I just dont think were there yet, Kahl said.

The Abrams tank is a very complicated piece of equipment. Its expensive. Its hard to train on. It has a jet engine.

Germany replaced its defence minister this week and said the tank decision is the first item on Pistorius agenda.

Ukraine, which has relied primarily on Soviet-era T-72 tank variants, says the new tanks would give its troops the mobile firepower to drive out Russian troops in decisive battles.

Western tanks have more effective armour and better guns than Soviet-era counterparts, which have been destroyed in their hundreds on both sides during the 11 months of war in Ukraine.

Fighting has been concentrated in the south and east of Ukraine after Russias initial assault from the north aimed at taking Kyiv was thwarted during the first months Russias special military operation.

After major Ukrainian gains in the second half of 2022, the front lines have largely been frozen in place over the past two months, with neither side making big gains despite heavy casualties in intense trench warfare.

The situation on the front line remains tough, Zelenskyy said in a video address on Wednesday.

We are seeing a gradual increase in the number of bombardments and attempts to conduct offensive actions by the invaders.