World leaders including Prime Minister Rishi Sunak, Ukraine's Volodymyr Zelenskyy and France's Emmanuel Macron are among those representing the 90 or so states participating in the event in Switzerland this weekend.

It comes as Ukrainian defenders continue to sustain heavy attacks from Russian forces, despite blunting a major assault on the city of Kharkiv in recent weeks.

On Friday, an attack on Russia's Belgorod region - just across the border from Ukraine - killed six people, according to Russian authorities.

The summit aims to pressure Russia into ending its war in Ukraine, but the absence of Moscow and its ally China may blunt its potential impact.

President Joe Biden will not attend the conference, with Vice President Kamala Harris making the trip instead.

"I must do everything in my power to get my husband back," says Svitlana Bilous. She is one of the many relatives of Ukrainian soldiers who have made the trip to Switzerland for the summit.

During the day's events, they will wave banners and shout slogans to try and raise awareness of the troops who have yet to come home.

Ms Bilous, 34, hails from Kharkiv in north-east Ukraine. She holds on to hope that her husband is still alive, but she has not had any information about him since he went missing in April last year.

Ukrainian officials said in February about 8,000 people - civilians and soldiers - are in Russian hands.

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Speaking at the summit, President Zelenskyy said: "Ukraine never wanted this war. It's a criminal and absolutely unprovoked aggression by Russia."

Experts and critics say little substance or few big breakthroughs are expected because Russia is not attending.

"The summit risks showing the limits of Ukrainian diplomacy," said Richard Gowan, UN Director at the International Crisis Group.

"Nonetheless, it is also a chance for Ukraine to remind the world that it is defending the principles of the UN Charter."

Russian President Vladimir Putin said on Friday that Russia would end the war in Ukraine only if Kyiv agreed to drop its NATO ambitions and hand over the entirety of four provinces claimed by Moscow - demands Kyiv swiftly rejected as tantamount to surrender.