A draft of the final summit declaration seen by Reuters refers to Russia's invasion as a "war", a label Moscow rejects, and calls for Ukraine's control over the Zaporizhzhia nuclear plant and its Azov Sea ports to be restored.
Moscow casts what it calls its special military operation in Ukraine as part of a broader struggle with the West, which it says wants to bring Russia to its knees. Kyiv and the West say Russia is waging an illegal war of conquest.
World leaders including US Vice President Kamala Harris, German Chancellor Olaf Scholz and French President Emmanuel Macron gathered this weekend at a mountaintop resort in a bid to bolster international support for ending the war.
Ukraine has rejected a Russian peace proposal requiring it to drop its ambitions to join NATO. (AP PHOTO)
Many Western leaders voiced forceful condemnation of the invasion, invoking the UN Charter in defence of Ukrainian territorial integrity, and rejecting Russian President Vladimir Putin's demands for parts of Ukraine as a condition for peace.
"One thing is clear in this conflict: there is an aggressor, which is Putin, and there is a victim, which is the Ukrainian people," Spanish Prime Minister Pedro Sanchez said.
Some leaders are expected to depart early, and talks on Sunday will turn towards pursuing a joint position on the need for nuclear and food security, and the return of prisoners of war and children removed from Ukraine during the conflict.
White House National Security Adviser Jake Sullivan told reporters Qatar had helped to mediate the return from Russia of 30 or more Ukrainian children to their families.
"It's going to take international pressure. It's going to take a spotlight from the international community, and not just from the voices from the United States or Europe, but from unusual voices, as well, to say what Russia has done here is morally reprehensible and must be reversed," he said.
Kyiv says about 20,000 children have been taken to Russia or Russian-occupied territory without the consent of family or guardians since the war began. Moscow rejects this, saying it has protected vulnerable children from the war zone.
The draft communique dated June 13 calls for all illegally deported children to be returned.
Delegates from around the world are working on the final declaration of the Ukraine peace summit. (AP PHOTO)
Ukrainian President Volodymyr Zelenskiy hailed the participation of more than 90 countries at the Buergenstock resort overlooking Lake Lucerne as a show of international support for Kyiv, even as some European allies said a broader outreach was needed to build a lasting peace plan.
One central ambition of the Swiss and Ukrainian organisers is to announce on Sunday the host country for a follow-up conference meant to build on the Swiss momentum.
Saudi Arabia is one of the favourites, and Foreign Minister Prince Faisal bin Farhan Al Saud said the kingdom was ready to assist the peace process, but warned that a viable settlement would hinge on "difficult compromise".
Striking a balance in the summit's final declaration between forthright condemnation of Russia's invasion of Ukraine and wording that commands the broadest possible support has been part of the diplomatic tug-of-war at the event, sources say.
It remains to be seen how many countries will back a final joint declaration, and Austrian Chancellor Karl Nehammer on Saturday sought to temper hopes somewhat.
"Just to manage expectations, please: the crucial take-away is that we've all come here, that we're talking, that many different nations and continents are talking to each other ... This is the essence of this conference," he said.
"Peace and peace processes take time, working millimetre by millimetre."
