Ukraine’s President Volodymyr Zelensky has issued a desperate invitation for Donald Trump to visit the war-torn country as his supporters in Congress continue to block the passage of a vital $60 billion military aid bill.

The move follows a meeting with US Vice-President Kamala Harris at which Zelensky pleaded for the additional support following a Russian offensive that forced Kyiv’s forces to abandon a key town in the country’s east.

“We are counting on this positive decision of the Congress,” Zelensky said after meeting Harris on Saturday, the second day of the Munich Security Conference, an annual gathering of top political and defence officials to debate international security policy.

The aid package remains stalled in the Republican-controlled House of Representatives, with critics charging Trump’s congressional allies are deliberately starving Ukraine of vital supplies to deny President Joe Biden a legislative victory ahead of November’s presidential election.

Republicans counter that the US has no way of checking if the funds are being stolen, insisting that America has more pressing problems on its southern border with Mexico.

Zelensky, at a joint press conference with Harris, said that for Ukraine “this package is vital”. His plea came as Ukraine’s army said it has withdrawn from Avdiivka in eastern Ukraine after months of heavy fighting.

The Ukrainian leader stressed that his country is depending on further support from its most important ally and is deeply grateful for previous aid.

‘I’m ready to go with him’

“If Mr Trump, if he will come, I’m ready even to go with him to the front line,” Zelensky said.

“We have to demonstrate (to) people who are decision-makers, what does it mean? The real war – not in Instagram, real war.”

NATO Secretary General Jens Stoltenberg more pointedly urged US Republican politicians to approve the military aid for Ukraine requested by Biden.

“Every week we wait means that there will be more people killed on the front line in Ukraine,” Stoltenberg said.

“So it’s not for me to give advice on how to pass legislation to the US Congress. But what I can say is the vital and urgent need for the US to decide on a package for Ukraine.”

After long delays, the Senate recently approved plans for new Ukraine aid worth about $US60 billion ($A92 billion).

But approval in the second chamber is uncertain – especially since Speaker Mike Johnson has said he won’t bring the bill to the floor.

Harris stressed the United States remained firmly behind Ukraine and Biden would continue fighting to deliver the needed aid to support the country in its battle against the ongoing Russian invasion.

F-16s on the way

Danish Prime Minister Mette Frederiksen criticised fellow supporters of Ukraine for being too slow and hesitant to supply the embattled country with the weapons it needs.

She said Denmark would soon deliver F-16 fighter jets to Ukraine and was still seeking more partners to supply the advanced fighter plans.

German Chancellor Olaf Scholz called on EU partners to follow Berlin’s example and ramp up aid for Ukraine, saying it was in member states’ own security interests to do so.

The discussions came one day after Russian dissident Alexei Navalny died in a Russian prison camp.

Many attendees at the conference and leaders elsewhere blamed Putin for his death.

-with AAP