US President Donald Trump is set to speak to Russian President Vladimir Putin on Monday about peace in Ukraine as European leaders demanded that the Kremlin accept an immediate ceasefire to halt the region's deadliest conflict since World War Two.

Putin sent thousands of troops into Ukraine in February 2022, triggering the gravest confrontation between Russia and the West since the 1962 Cuban Missile Crisis.

Trump, who says he wants to be remembered as a peacemaker, has repeatedly called for an end to the "bloodbath" of Ukraine, which his administration casts as a proxy war between the United States and Russia.

Under pressure from Trump, delegates from the warring countries met last week in Istanbul for the first time since March 2022, after Putin proposed direct talks and Europeans and Ukraine demanded an immediate ceasefire.

"The subjects of the call will be stopping the 'bloodbath' that is killing, on average, more than 5,000 Russian and Ukrainian soldiers a week, and trade," Trump wrote on his Truth Social website.

"Hopefully it will be a productive day, a ceasefire will take place, and this very violent war, a war that should have never happened, will end."

Trump, who said that progress on peace was unlikely until he and Putin get together, said he would speak to Putin at 10 am Eastern Time (1400 GMT) on Monday.

The Kremlin said preparations for a call were underway.

Trump, whose administration has made clear that Russia could face additional sanctions if it does not take peace talks seriously, said he would also speak to Ukrainian President Volodymyr Zelenskiy and various members of NATO.

Putin, whose forces control a fifth of Ukraine and are advancing, has stood firm on his conditions for ending the war, despite public and private pressure from Trump and repeated warnings from European powers.

On Sunday, Russia launched its largest drone attack on Ukraine since the start of the war.

Ukraine's intelligence service said it also believed Moscow intended to fire an intercontinental ballistic missile on Sunday, though there was no confirmation from Russia.

In June 2024, Putin said Ukraine must officially drop its NATO ambitions and withdraw its troops from the entire territory of the four Ukrainian regions Russia claims.

On Sunday, British Prime Minister Keir Starmer discussed Russia's war against Ukraine with leaders of the United States, Italy, France and Germany, a Downing Street spokesperson said.

"Tomorrow, President Putin must show he wants peace by accepting the 30-day unconditional ceasefire proposed by President Trump and backed by Ukraine and Europe," French President Emmanuel Macron said on X after Sunday's call.

Putin is wary of a ceasefire and says fighting cannot be paused until a number of crucial conditions are worked out or clarified.

European leaders say Putin is not serious about peace, though they fear Trump and he may force a punitive peace deal that will leave Ukraine essentially shorn of a fifth of its territory and lacking a strong security guarantee against possible future attack from Russia.

Former US President Joe Biden, Western European leaders and Ukraine cast the invasion as an imperial-style land grab and repeatedly vowed to defeat Russian forces which they say could one day attack NATO, a claim denied by Moscow.

Putin casts the war as a watershed moment in Moscow's relations with the West, which he says humiliated Russia after the 1991 fall of the Soviet Union by enlarging NATO and encroaching on what he considers Moscow's sphere of influence, including Ukraine.