Ukraine won't give up land to Russia, President Volodymyr Zelensky warned early on Saturday, hours after Washington and Moscow agreed to hold a summit in a bid to end the war.

Presidents Vladimir Putin and Donald Trump will meet in the far-north US state of Alaska, near Russia, on August 15, to try to resolve the three-year conflict, despite multiple warnings from Ukraine and Europe that Kyiv must be part of the negotiations.

Announcing the summit on Friday, Trump said that "there'll be some swapping of territories to the betterment of both" Ukraine and Russia, without providing further details.

However, Zelensky said that "any decisions against us, any decisions without Ukraine, are also decisions against peace. They will achieve nothing."

The war, he added, "cannot be ended without us, without Ukraine".

Three rounds of negotiations between Russia and Ukraine this year have failed to bear fruit, and it remains unclear whether a summit would bring peace any closer.

Tens of thousands of people have been killed since Russia launched its full-scale invasion of Ukraine in February 2022, with millions forced to flee their homes. (AFP)