"Pressure must be exerted on Russia for the sake of a fair peace. We must learn from the experience of Ukraine and our partners to prevent deception on the part of Russia," Zelensky wrote on social media.

"There are currently no signs that the Russians are preparing to end the war," he added.

Zelensky is due in Berlin on Wednesday for talks with European leaders and Trump ahead of the US president's summit with Russian counterpart Vladimir Putin.

The Ukrainian leader said he and his team had held more than 30 conversations with world leaders and high-ranking officials ahead of the talks.

The flurry of diplomatic engagements have been overshadowed by rapid, but so far limited Russian push in the eastern Donetsk region, which the Kremlin claims is part of Russia.

A member of the Ukrainian delegation travelling with Zelensky to Berlin told AFP that the Russian gains around the mining hub of Dobropillia "did not influence" preparation for Wednesday's talks.

Zelensky conceded one day earlier that Russian forces had advanced by up to 10 kilometres (six miles), but ruled out swapping territory with Moscow as part of any deal with Russia.