Ukrainian President Volodymyr Zelensky is joining European leaders in talks aimed at increasing pressure on US President Donald Trump to side with Ukraine during Friday’s summit with his Russian counterpart in Alaska.

In an online call with Trump on Wednesday, the leaders are expected to reiterate that no decisions should be taken without Ukraine, including changing its borders by force.

Trump has said any peace deal would involve “some swapping of territories” and it is believed one of Russian President Vladimir Putin’s demands is that Kyiv surrenders the parts of the Donbas it still controls.

On Tuesday, Zelensky said such a concession could be used as a springboard for future attacks by Russia, which has been making gains recently.

Russia launched a full-scale invasion of Ukraine in February 2022.

A Russian summer offensive has been progressing with troops making a sudden thrust near the eastern town of Dobropillia and advancing 10km (six miles) in a short period of time.

While downplaying Russia’s advance, Zelensky said it was “clear to us” that Moscow’s objective was to create a “certain information space” before Putin meets Trump that “Russia is moving forward, advancing, while Ukraine is losing”.

No official details have emerged on what demands Putin could make when he meets Trump in Anchorage on Friday.

The Donbas – made up of the eastern regions of Luhansk and Donetsk – has been partly occupied by Russia since 2014.

Moscow now holds almost all of Luhansk and about 70% of Donetsk but speaking to reporters on Tuesday, Zelensky reaffirmed that Ukraine would reject any proposal to leave the Donbas.

Zelensky has previously insisted that Ukrainians would not “gift their land to the occupier”, and pointed to the country’s constitution, which requires a referendum before a change in its territory.

Last week, Trump said there would be “some swapping of territories to the betterment of both” Russia and Ukraine – sparking concern in Kyiv and across Europe that Moscow could be allowed to redraw Ukraine’s borders by force.

Russia currently controls just under 20% of Ukrainian territory.

The White House on Tuesday said the Alaska talks would be a “listening exercise” for Trump and added having him and Putin sit down in the same room would give the US president “the best indication on how to end this war”.

It follows Trump describing the summit as a “feel-out meeting” on Monday, seeming to tone down expectations that Friday’s meeting could bring Ukraine and Russia closer to peace.

When he announced the summit last week, Trump sounded positive that the meeting could result in concrete steps towards peace.

“I think my gut instinct really tells me that we have a shot at it,” he said.

The Ukrainian leader has previously said any agreements without Kyiv’s involvement would amount to “dead decisions”.