President Volodymyr Zelensky appealed on Friday to Ukraine's backers for additional weapons as Kyiv faces advancing Russian forces in the east and devastating strikes by Moscow.

The Ukrainian leader pressed his nation's case to allies meeting at Ramstein Air Base in Germany, where Washington unveiled a new US$250 million in military aid.

"We need more weapons to drive Russian forces off our land," said Zelensky, who also met with German Chancellor Olaf Scholz and was to head to Italy for talks.

The gathering comes as Moscow's forces advance in the Donbas region, with Russian President Vladimir Putin on Thursday declaring that capturing the eastern area was his "primary objective" in the conflict.

Zelensky urged Kyiv's supporters to follow through on previous commitments, saying: "The number of air defence systems that have not been delivered is significant."

The Ukrainian leader again called for restrictions to be lifted on the use of long-range Western weapons to hit targets inside Russia.

"We need to have this long-range capability, not only on the occupied territory of Ukraine, but also on the Russian territory," Zelensky said.

In Italy, Zelensky is due to hold talks with Prime Minister Giorgia Meloni and attend The European House-Ambrosetti forum in Cernobbio, on Lake Como.

Hungarian Prime Minister Viktor Orban – who upset his EU counterparts and Zelensky by meeting Putin in Moscow in July – is also attending the three-day economic forum.

Italy has strongly supported Ukraine and has sent weapons to help it defend itself against Russian forces, while insisting these must only be used on Ukrainian soil.

At the meeting at the US base in Germany, US defence chief Lloyd Austin announced that Washington will provide US$250 million in new military aid for Ukraine.

The package "will surge in more capabilities to meet Ukraine's evolving requirements," Austin told the meeting.

The assistance is expected to include ammunition for Himars precision rocket launchers, artillery rounds, anti-tank and anti-air weapons, a US defence official said on condition of anonymity.

The talks in Germany, with representatives from some 50 nations, were to focus on areas including bolstering Ukraine's air defences and encouraging allies to boost their defence industries, Pentagon spokesman Major General Pat Ryder said ahead of the meeting. (AFP)