German Chancellor Olaf Scholz will host his French and Polish counterparts in Berlin on Friday in a bid to project European unity on support for Ukraine after weeks of friction between the allies.

A hastily arranged summit in Paris last month had aimed to give fresh impetus to stagnating Western efforts to help Ukraine repel a full-scale Russian invasion that has entered its third year.

Instead French President Emmanuel Macron's refusal to rule out deploying Western troops to Ukraine triggered a dressing down from Scholz, highlighting long-running divisions between the European Union's two top powers.

The European spat comes as U.S. support for Ukraine is also weakening, highlighting a Western leadership vacuum that risks further emboldening Russian President Vladimir Putin, say diplomats.

"The time has come for calm between France and Germany," former French Foreign Minister Jean-Yves Le Drian, who is now a special envoy for Macron, told FranceInfo radio on Thursday. "I think that this meeting will help ease tensions and strengthen support for Ukraine."

Macron is expected to arrive around midday for a bilateral with Scholz before Tusk's arrival around 1400 local time (1300 GMT), a government official said. The three leaders will make statements before holding a meeting together.

Franco-German spats are nothing new. But the current level of discord has alarmed officials in Kyiv and across the continent.

The two leaders are sending very different strategic messages. Macron sounds more hawkish these days while Scholz's supporters present him as a “peace chancellor” who will avoid any escalation towards a war between NATO and Russia.

Mykhailo Podolyak, a senior adviser to Ukrainian President Volodymyr Zelenskiy, told Reuters that "indecision and uncoordinated action" among Kyiv’s allies was leading to "grave consequences". "Russia starts to get cocky and begins to believe that it can quantitatively squeeze Ukraine," he said. "Ukraine, in turn, is experiencing a severe shortage of specific resources, primarily shells, and is partially losing the initiative."

SEARCH FOR AMMUNITION U.S. President Joe Biden has been unable to get a big Ukraine aid package through Congress, and much of his foreign policy energy is focused on the war in Gaza. At home, an election rematch with Donald Trump looms large.

At the summit in Paris and a follow-up ministerial meeting, Washington only sent its assistant secretary of state for European and Eurasian affairs. That makes Kyiv's European allies - and their ability to work together effectively - all the more critical, with ammunition-starved Ukrainian troops facing their toughest battles since the early days of Russia's invasion.

NATO Secretary General Jens Stoltenberg issued a stark warning to members of the alliance on Thursday that Ukraine was running out of ammunition and they were not doing enough to help.

"It is an urgent need for allies to make the decisions necessary to step and provide more ammunition to Ukraine. That's my message to all capitals," Stoltenberg said.

Polish Prime Minister Donald Tusk told state-news channel TVP Info that he will be able to report back to Scholz and Macron about his meetings with Biden and other U.S. leaders in Washington this week.

Tusk underscored the importance of revitalizing the so-called Weimar Triangle of cooperation between Warsaw, Berlin and Paris, after eight years of nationalist rule in Poland that had strained those relations.

Poland's strategic location neighboring Ukraine has made it a vital partner in Europe's quest to support Kyiv.

Still, questions over weapons supplies and also whether Ukraine has the forces to face Russia in the long term has left some allies wavering in their support.

"There are some who do not believe Ukraine will win the war now and think that Europe is not capable of getting the long-term support Ukraine needs and consider that the U.S. cannot be counted upon," said one European diplomat.

(Reporting by John Irish, Andrew Gray and Sarah Marsh; additional reporting by Pavel Polityuk in Kyiv, Alan Charlish in Warsaw and Andreas Rinke in Berlin; editing by Jonathan Oatis)