Leaders of France, Germany and Britain will host a video call on Sunday for their so-called "coalition of the willing" to discuss steps towards ending the war in Ukraine, after Donald Trump dropped his push for a ceasefire after his Alaska summit with Russian leader Vladimir Putin.

Securing a ceasefire in Ukraine, more than three years after Russia's invasion, had been one of the US president's core demands before the summit, to which Ukraine and its European allies were not invited.

But after a meeting that yielded no clear breakthrough, Trump ruled out an immediate ceasefire in Ukraine, a move that would appear to favor Putin who has long argued for negotiations on a final peace deal.

Ukraine and its European allies have criticized it as a way to buy time and press Russia's battlefield advances.

Trump spoke with Zelensky and European leaders on his flight back from Alaska to Washington, saying afterward that "it was determined by all that the best way to end the horrific war between Russia and Ukraine is to go directly to a peace agreement which would end the war."

Ceasefire agreements "often times do not hold up," Trump added on his Truth Social platform.

But Zelensky, who is due to visit Washington on Monday, appeared unconvinced by the change of tack, saying on Saturday that it "complicates the situation".

If Moscow lacks "the will to carry out a simple order to stop the strikes, it may take a lot of effort to get Russia to have the will to implement far greater -- peaceful coexistence with its neighbors for decades," he said on social media.

Trump expressed support during his call with Zelensky and European leaders for a proposal by Putin to take full control of two largely Russian-held Ukrainian regions in exchange for freezing the frontline in two others, an official briefed on the talks told AFP.

Putin "de facto demands that Ukraine leave Donbas," an area consisting of the Donetsk and Lugansk regions in eastern Ukraine, the source said.

In exchange, Russian forces would halt their offensive in the Black Sea port region of Kherson and Zaporizhzhia in southern Ukraine, where the main cities are still under Ukrainian control.