Vice President Kamala Harris said calls for Ukraine to cede territory to Russia were “dangerous and unacceptable” as she met with Ukrainian President Volodymyr Zelensky on Thursday.

The comments from the Democratic presidential nominee were thinly veiled criticism of suggestions from Republican candidate Donald Trump and his running mate, JD Vance, that Ukraine should quickly cut a deal to end the war.

“They are not proposals for peace,” Ms Harris said. “Instead they are proposals for surrender.”

US support for Ukraine faces a partisan reckoning in this year’s presidential election, with Mr Trump criticising billions of dollars in military assistance and Ms Harris pledging to continue helping the besieged country.

Ms Harris’ meeting with Mr Zelensky came shortly after the Ukrainian leader sat down with President Joe Biden, who announced billions of dollars more in missiles, drones, ammunition and other supplies.

The weapons include an additional Patriot missile defence battery and a new shipment of glide bombs that can be deployed from Western fighter jets, increasing their strike range.

Mr Biden pledged to ensure that all approved funding is disbursed before he leaves office, and he said he plans to convene a meeting with other world leaders focused on Ukraine’s defence during a visit to Germany next month.

“We stand with Ukraine, now and in the future,” Mr Biden said, alongside Mr Zelensky in the Oval Office. “Russia will not prevail. Ukraine will prevail.”

Meanwhile, Mr Zelensky’s tumultuous relationship with Mr Trump continued to deteriorate this week.

Instead of meeting with Mr Zelensky, Mr Trump criticised him.

As for US support for Ukraine, Mr Trump complained that “we continue to give billions of dollars to a man who refuses to make a deal” to end the war.

His message dovetails with Russian propaganda that claims intransigence by Kyiv — not aggression from Moscow — has prolonged the bloodshed.

It’s the most politically treacherous landscape that Mr Zelensky has encountered in Washington since Russia invaded nearly three years ago.

Ukrainian officials are anxious to maintain good relations with whoever becomes the next president of the United States, which is its biggest and most important provider of arms, money and other support.

But the effort risks slipping into the political blender of the presidential campaign, polarising the discussion around a war that used to be a bipartisan cause celebre in Washington.

On Thursday, Mr Zelensky found some bipartisan support as he visited Capitol Hill, where he was greeted by Senate Majority Leader Chuck Schumer and Senate Minority Leader Mitch McConnell.

Senator Lindsey Graham, a South Carolina Republican, said Mr Zelensky asked to use long-range weapons, such as British-supplied Storm Shadow missiles or US-made ATACMS, for “maximum benefit to bring (Russian President Vladimir) Putin to the table” and increase Ukraine’s negotiating position.

“If we don’t make that fundamental choice this week, I think the outcome for Ukraine is dire,” Mr Graham said.

Administration officials have been sceptical of Mr Zelensky’s request, believing the weapons could have limited benefits but increase the risk of escalating the conflict.

Richard Blumenthal, a Connecticut Democrat, said senators gave Mr Zelensky advice on how to persuade Mr Biden to loosen restrictions.

Jim Himes, another Connecticut Democrat and the ranking member of the House Permanent Select Committee on Intelligence, said Mr Zelensky wanted “more, faster”.

“He was politely frustrated,” Mr Himes said and specifically requested more Patriot missile defences as Russia escalates strikes on Ukraine’s cities and energy grid before the winter.

Mr Zelensky’s trip to Washington coincides with the annual meeting of the UN General Assembly in New York, where the Ukrainian leader spoke on Wednesday.

Last week, Mr Trump said he would “probably” meet with Mr Zelensky while he was in the US, but a senior campaign official said there was never a meeting on the books.

The official said Mr Trump had told Mr Zelensky back in July that it would probably be better not to sit down together until after the election. An aide for Mr Zelensky did not respond to questions about the potential meeting.

Mr Trump was impeached during his first term for asking Mr Zelensky for help investigating Mr Biden, then a candidate for the Democratic presidential nomination, at a time when the Ukrainian leader was seeking support from Washington.

Now there are fears that Mr Trump would cut off or add strings to US military assistance if he returned to the White House.

Mr Trump has also spoken admiringly about Mr Putin, and this week he praised Russia’s record of winning wars.

Mr Zelensky can expect a far different tone from Ms Harris, who met with him in Munich just days before Russia invaded.

During her debate with Mr Trump earlier this month, she expressed pride in US support for Ukraine’s “righteous defence”.

“If Donald Trump were president, Putin would be sitting in Kyiv right now,” she said.