Ukraine says it expects strong decisions from NATO and other countries that are meeting to discuss whether to send modern battle tanks and the United States says it's time to "dig deeper" to help Kyiv confront Russian forces.
The defence ministers' talks at Ramstein Air Base in Germany follow Ukrainian warnings that Russia is seeking to re-energise its almost 11-month-old invasion after unilaterally annexing parts of Ukraine's east and south it does not fully control.
The United States and Finland announced new military aid before Friday's gathering, where the main focus will be whether Germany will allow the supply to Ukraine of its Leopard 2 tanks used by armies across Europe.
Ukrainian President Volodmyr Zelenskiy, speaking at the start of the meeting, thanked allies for their support, but said more was needed and more quickly to defeat Russia's invasion.
"We have to speed up. Time must become our weapon. The Kremlin must lose," Zelenskiy said.
Russia was regrouping, recruiting, and trying to re-equip, US Defense Secretary Lloyd Austin said.
"This is not a moment to slow down. It's a time to dig deeper. The Ukrainian people are watching us," he told the meeting, without making specific reference to tanks.
Berlin has veto power over any decision to export the tanks and Chancellor Olaf Scholz's government has appeared reluctant to authorise that for fear of provoking Russia.
The Kremlin reiterated that Western countries supplying tanks to Ukraine would not change the course of the conflict but would add to the problems of the Ukrainian people.
Some allies, along with Ukraine, say Germany's concern is misplaced with Russia already fully committed to war.
"We are, in fact, now waiting for a decision from one European capital, which will activate the prepared chains of co-operation regarding tanks," Zelenskiy said in a separate address late on Thursday.
"We are expecting strong decisions."
Lithuania, which fears for its own future if Russia overruns Ukraine, said on Thursday that several countries would announce sending the Leopard tanks to Ukraine at the meeting.
"Some of the countries will definitely send Leopard tanks to Ukraine, that is for sure," Defence Minister Arvydas Anusauskas told Reuters about the Ramstein pledges, speaking after 11 nations met in Estonia on Thursday and pledged new military aid.
A German military source said later that Germany had yet to receive any request for permission to re-export German-made Leopard tanks to Ukraine.
Finland pledged more than 400 million euros ($A625 million) worth of extra defence equipment for Ukraine and has indicated it could add Leopard tanks if there was an agreement with allies.
Polish Prime Minister Mateusz Morawiecki said he was "moderately pessimistic" Berlin would give the green light. His government has suggested Poland may go ahead anyway.
Ukraine and Russia have both relied primarily on Soviet-era T-72 tanks, which have been destroyed in their hundreds during the war that Russian President Vladimir Putin started on February 24, calling it a "special military operation" to protect Russia and Russian speakers.
Ukraine and its allies accuse Russia of an unprovoked war to grab territory.
The United States on Thursday announced new military aid valued up to $US2.5 billion ($A3.6 billion), including hundreds of armoured vehicles and support for air defences.
The package makes a total of more than $US27.4 billion in US security aid.
A government source in Germany has said it would move on the Leopard tanks issue if the United States agrees to send Abrams tanks to Ukraine. Abrams tanks were not included in Thursday's US announcement.
Germany's new defence minister, Boris Pistorius, said earlier, however, that he did not know of any requirement that Ukraine receive US and German tanks simultaneously, leaving open the possibility of an agreement on Friday.
Fighting has been most intense in Ukraine's eastern Donbas region, which Russia claimed to have annexed in September along with two regions in the south.
On Friday, Russian proxy forces in eastern Ukraine said Russian forces had taken control of Klishchiivka, a small settlement south of Bakhmut, a day after Russia's Wagner mercenary group made the same claim.
Ukrainian military analyst and reserve Colonel Roman Svitun refuted that claim on Thursday evening.