U.K. Prime Minister Keir Starmer has told allies to “keep the pressure” on Russian President Vladimir Putin to back a ceasefire in Ukraine, hailing Ukraine as the “party of peace.”

In his opening remarks Saturday, Starmer said Putin will “sooner or later” have to “come to the table.”

Unlike the first summit on March 2, the meeting of what Starmer has termed the “coalition of the willing” is being conducted virtually. The call is expected to delve into how countries can help Ukraine militarily and financially as well as gauging support for any future possible peacekeeping mission in the event Putin backs a cessation of hostilities.

“My feeling is that sooner or later he’s going to have to come to the table and engage in serious discussion, but — this is a big but for us this morning in our meeting — we can’t sit back and simply wait for that to happen,” Starmer told leaders while sitting in front of a screen in an office in 10, Downing Street.

“I think that means strengthening Ukraine so they can defend themselves, and strengthening, obviously, in terms of military capability, in terms of funding, in terms of the provision of further support from all of us to Ukraine.”

Around 25 countries are expected to be involved in the call, including European partners such as France and Italy, and Ukraine. Leaders from Australia, Canada and New Zealand, as well as officials from NATO and the European Union’s executive, are also set to take part. The United States is not represented at the meeting.

Saturday’s meeting takes place in the wake of a U.S. proposal for a 30-day ceasefire in Ukraine, which Ukrainian President Volodymyr Zelenskyy has backed. Putin has indicated that he supports a truce in principle but has set out a host of details that need to be clarified before agreeing to a ceasefire.

“President Zelensky, who’s with us this morning, has shown once again that Ukraine is the party of peace, because he has agreed to and committed to a 30-day unconditional ceasefire,” Starmer said. “Now what we see, and this is centerpiece for our discussions today, is that Putin is the one trying to delay.”

The United States has shifted its approach on the war since the return of President Donald Trump to the White House. The change of approach relative to that taken by Trump’s predecessor, Joe Biden, became particularly notable after Trump clashed with Zelenskyy on Feb. 28 in the Oval Office.

Trump voiced optimism Friday that Putin, who met with U.S. envoy Steve Witkoff earlier in the week, will back a ceasefire.

“I’m getting from the standpoint about a ceasefire and ultimately a deal some pretty good vibes coming out of Russia,” he said.

Starmer has taken the lead, along with French President Emmanuel Macron, in assembling the “coalition of the willing,” in part to persuade Trump to maintain support for Kyiv. One outcome has already been a growing acceptance from European countries in particular that they need to do more to ensure their own security, including by increasing their defense spending.

Images from the Elysee showed Macron and his aides listening to Starmer’s opening statement in a room of the French presidential palace.

Ukraine, under severe military pressure on parts of the front line three years after Russia’s full-scale invasion, has already endorsed the truce proposal. Russia’s army has gained battlefield momentum, and analysts say Putin likely will be reluctant to rush into a ceasefire while he feels he has an advantage.

Starmer said that if Putin is “serious about peace,” he has to “stop his barbaric attacks” on Ukraine and agree to a ceasefire.

“The world is watching,” he said.