Ukrainian President Volodymyr Zelensky has said that he expected "strong decisions" on further Western arms supplies at a key meeting of allies at the US Ramstein airbase in Germany tomorrow.

It comes as the United States and Germany tried to resolve a stand-off that has so far prevented the West from sending heavy tanks to Ukraine, while Kyiv pleaded for the weapons help it to turn the tide against Russian forces.

"As we prepare for tomorrow's Ramstein, we expect strong decisions. We expect a powerful military support package from the United States," Mr Zelensky said.

US Defense Secretary Lloyd Austin and Germany's new Defence Minister Boris Pistorius talked in Berlin just hours after Mr Pistorius was sworn into office.

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 tomorrow at Ramstein, Washington's main European air base.

Billions of dollars worth of military aid is expected to be pledged at the Ramstein meeting, billed as a chance for the West to give Ukraine what it needs to defeat Russia in 2023.

Countries including Canada, the Netherlands and Sweden have already announced armoured vehicles and air defences.

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But the big question will be whether the meeting brings heavy tanks, which Kyiv says it needs to fend off Russian assaults and recapture occupied land.

"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.

"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 shouldn't be like that."

Berlin has so far blocked allies from sending its Leopard 2 tanks, workhorse of militaries across Europe.

A Leopard 2A6 tank of the German armed forces seen during a NATO military exercise

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 they have no plans yet to send the Abrams, which runs on powerful turbine engines seen as using too much fuel for Kyiv's strained logistics system to supply at the front.

Mr Pistorius and Mr Austin both spoke about the importance of supporting Ukraine ahead of their meeting, but neither addressed the tank issue directly.

Lloyd Austin (L) and Boris Pistorius had talks in Berlin

At a ceremony after being sworn in, Mr Pistorius said: "These are not normal times, we have a war raging in Europe. Russia is waging a brutal war of annihilation on a sovereign country, on Ukraine."

Mr Austin described Germany as one of Washington's closest allies and thanked it for its support for Ukraine so far.

Poland and Finland have already said they would send Leopards if Germany lifts its veto. In a sign of mounting frustration, Poland suggested it might do so even if Germany tries to block it.

"Consent is of secondary importance here. We will either obtain this consent quickly, or we will do what is needed ourselves," Prime Minister Mateusz Morawiecki told private broadcaster Polsat News last night.

Russia has responded to the prospect of more weapons for Kyiv with threats of escalation.

Dmitry Medvedev, a Vladimir Putin ally who stood in as president from 2008-2012 when Mr Putin took a hiatus to act as prime minister, made one of Moscow's clearest threats to use nuclear weapons if it loses in Ukraine.

"The defeat of a nuclear power in a conventional war may trigger a nuclear war," Mr Medvedev said. "Nuclear powers have never lost major conflicts on which their fate depends."

German Chancellor Olaf Scholz, has been reluctant to send weapons seen as provoking Moscow. Many of Berlin's Western allies say that concern is misplaced, with Russia already fully committed to war.

There have been signs of friction within Germany's governing coalition. Mr Scholz's deputy Robert Habeck, from his coalition partners The Greens, said just last week that Germany would not stand in the way of other countries sending Leopards to Ukraine.

Marie-Agnes Strack-Zimmermann, from the coalition's third party the centrist Free Democrats, said Mr Scholz must be careful to avoid dividing Europe.

"This can be done with a clear message to Vladimir Putin. Anyone who wants to destroy our system will have to deal with all of us democrats," she said.

Tying the Leopards to US Abrams tanks could shift the onus onto Washington. Colin Kahl, the Pentagon's top policy adviser, has said the Abrams tanks were not likely to be included in Washington's next massive $2 billion military aid package, to be headlined by Stryker and Bradley armoured vehicles.

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

Ukraine and Russia have both relied primarily on Soviet-era T-72 tanks, which have been destroyed in their hundreds in 11 months of fighting.

A Ukrainian tank is off loaded along a road outside of the strategic city of Bakhmut

Kyiv says better armed and protected Western tanks would give its troops the mobile firepower to drive out Russian troops in decisive battles.

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

Yevgeny Prigozhin, leader of the private Russian mercenary force Wagner which has taken a leading role in fighting near the eastern city of Bakhmut, claimed today that his forces had seized the village of Klishchiivka on Bakhmut's outskirts.

Kyiv has previously denied that the settlement has fallen. Reuters could not confirm the situation there.

EU parliament urges creation of special tribunal for Ukraine

The European Parliament called for a special tribunal to be set up that could try Russian President Vladimir Putin for the crime of aggression against Ukraine.

The non-binding resolution - backed by a large majority of MEPs - said there was an "urgent need" for the EU and its member states to push for the establishment of the court.

It said the tribunal should have jurisdiction to investigate not only Mr Putin and Russia's leadership, but also Belarusian President Alexander Lukashenko for aiding Moscow.

Kyiv is pushing the international community to set up a tribunal that could more easily target the top Russian officials over the war on Ukraine.

President Zelensky welcomed the move by the parliament and called "on all our partners to support such a tribunal".

"Russia must be held accountable for its war of aggression and justice must prevail," the Ukrainian leader wrote on Twitter.

Kyiv says a special tribunal is needed to overcome the fact that the International Criminal Court (ICC) - which has opened an investigation into the conflict - cannot prosecute Russia for the crime of aggression.

The EU executive floated a proposal for a specialised tribunal to target the leadership in Moscow in November, but so far there is no consensus within the bloc on its establishment.

Germany on Monday became the latest member state to support calls for a tribunal.

The EU's justice commissioner Didier Reynders said this week that Brussels was in discussions about establishing an international prosecution office as a step towards setting up the tribunal.