Kiev, Ukraine - At the time of unity in Kiev on Saturday, leaders from four major European countries threatened to increase pressure if Russian President Vladimir Putin does not accept an unconditional 30-day ceasefire.

Leaders from France, Britain, Germany and Poland said the proposal to start a ceasefire on Monday was supported by U.S. President Donald Trump, who briefed them on the phone earlier that day. Their statement is in an ongoing effort to convince Moscow to agree to a truce, which would allow the end of three years of full-scale war.

The demand announced in a joint press conference with Ukrainian President Volodymyr Zelenskyy that it would lead the so-called "willing alliance": a group of groups with more than 30 countries that promise to strengthen Ukraine to stop Russian aggression. They include French President Emmanuel Macron, British Prime Minister Keir Starmer, German Chancellor Friedrich Merz and Polish Prime Minister Donald Tusk, who traveled together for the first time on Saturday.

The ceasefire will cease fighting on land, sea and air. If Putin fails to comply, leaders threaten to strengthen sanctions, including Russia's energy and banking sectors.

Earlier in the day, Ukrainian Foreign Minister Andrii Sybiha said Kiev and its allies were ready for a "completely unconditional ceasefire" with Russia, starting on Monday for "at least 30 days." He added that four visiting leaders, Zelenskyy, made a "constructive" call with Trump.

Saturday marked the last day of a three-day ceasefire announced by Russia, with Ukraine saying Kremlin troops were repeatedly violated.

In March, the United States proposed a direct limited 30-day truce, which Ukraine accepted, but the Kremlin was already more satisfied.

European leaders said on Saturday that building Ukraine's military capabilities would be a key deterrent to Russia. This will require a powerful number of weapons to be provided to Ukraine to stop future attacks and invest in its defense sector. Macron said troops composed of foreign forces could also be deployed as "reliance" measures.

The French president added that with the support of European countries, the United States will lead monitoring of the proposed ceasefire and threaten “large-scale sanctions between Europeans and Americans…prepare and coordinate” if Russia violates the ceasefire.

But he said details about the potential deployment of Europe to Ukraine are still on the microscope. There is no mention of NATO membership, which remains the top choice for Kiev security guarantees.

Ukraine's Sybiha told reporters at the event that the top priority is to make Russia continue to fight.

Lieutenant General Keith Kellogg, who retired special envoys for Ukraine and Russia, said on Saturday that a "full" 30-day ceasefire covering air, land, ocean, ocean and infrastructure attacks "will begin the process of ending the largest and longest war since Europe."

Earlier on Saturday, European leaders attended a ceremony at Kiev’s Independence Square, marking the 80th anniversary of the end of World War II. They lighted candles with Zelenskyy in a temporary flag memorial, and Ukrainian soldiers and civilians have been killed since the Russian invasion.

Trump has urged the two sides to quickly reach a deal to end the war, but Russia has not signed it yet despite Zelensky agreeing to the 30-day plan for the U.S. to stop hostilities initially. Instead, it has been attacking about 1,000 miles (1,600 kilometers) of frontlines, including a deadly strike on residential areas without obvious military targets.

On Saturday morning, local officials in the northern part of Ukraine Sumi said that in the past day, Russian shelling killed three residents and injured four more. Another civilian man died on Saturday in a Russian drone, according to regional governor Oleksandr Prokudin.

French President Emmanuel Macron said in a speech at Kyiv reporter: "The situation in Poland, Germany and the UK is a historic moment of European defense, and has taken greater independence to our security. Obviously, for Ukraine and all of us, this is a new era. It is a new era. It is a European power in itself."

Trump said last week that he suspected Putin wanted to end his war in Ukraine and expressed new suspicion that a peace deal could be reached as soon as possible and hints further sanctions against Russia.

In the months since Trump returned to the White House, progress to end the war seems elusive, and his previous claims about an upcoming breakthrough failed to come true. Trump had previously pushed Ukraine toward Russian territory to end the war and threatened to walk away when the deal became too difficult.

Ukraine's European allies believe its fate is the basis for security on the African continent, and pressure is increasingly looking for ways to support Kiev, regardless of whether Trump withdraws or not.