EU chief Ursula von der Leyen on Friday announced plans for Brussels to lend Ukraine 35 billion euros backed by revenues of frozen Russian assets and promised to help Ukraine "keep warm" ahead of a third winter of war with Russia.

Von der Leyen was in Kyiv after a summer of intense fighting and as fears grow for how Ukraine's war-battered energy grid will cope this winter.

The International Energy Agency has said Kyiv faces its "sternest test" so far this winter, with Moscow expected to launch another bombing campaign on the country's already damaged infrastructure.

Von der Leyen's trip also came ahead of Ukraine President Volodymyr Zelensky's trip to the United States to present plans to end two and a half years of war.

"The European Union is here to help you in this challenge to keep the lights on, to keep your people warm and keep your economy going as you fight for your survival," von der Leyen said.

"We are now confident that we can deliver this loan to Ukraine very quickly, a loan that is backed by the windfall profits from immobilised Russian assets," she added, speaking alongside Zelensky.

Ukraine is desperate for funds as it seeks to prop up its economy and keep its electricity grid functioning.

The EU's proposal – which needs to be signed off by member states – is part of a bigger plan agreed by G7 powers in June to use the proceeds of frozen Russian assets to lend Kyiv US$50 billion.

The EU has frozen roughly US$235 billion of Russian central bank funds since the Kremlin launched its offensive in Ukraine in 2022, the vast bulk of immobilised Russian assets worldwide.

Von der Leyen also said Brussels would help "repair the damages done by the Russian strikes" to Ukrainian energy infrastructure.

"We will aim to restore 2.5 gigawatt of capacity this winter, that is approximately 15 percent of your country's needs for this winter," she said.

Zelensky praised the measures in his evening address.

"In everything from defence to social issues, we have really good results. Ursula, thank you," he said.

Norway later announced it would increase civilian aid to Ukraine by US$475 million and extend its aid package by three years to 2030.

"We are living through a very dangerous situation in Europe," said Prime Minister Jonas Gahr Store.

Zelensky is expected to present his so-called "victory plan" to end the fighting to US President Joe Biden during next week's visit.

"I really hope that he will support this plan," Zelensky said.

"The plan is designed for decisions that will have to happen from October to December... We would like that very much. Then we believe that the plan will work," he added.

He is due to meet Biden and the Democrats' presidential candidate Kamala Harris. Kyiv says he will also meet her Republican election rival Donald Trump.

Zelensky has said he aims to host another international peace summit outlining his vision to end the war in November, to which Russia will be invited.

His proposals will come after Ukraine's surprise incursion into Russia in August, where they still hold vast swathes of territory – and as Moscow's forces advance towards the city of Pokrovsk in eastern Ukraine. (AFP)