Ukraine's president said Kyiv would not allow Russian forces to regroup after their withdrawal from Kherson, and would not compromise Ukraine's sovereignty or territory.
Ukrainian President Volodymyr Zelenskyy has urged world leaders to back a plan to end the war in his country, saying now was the time to push for peace after Russia's defeat in the southern city of Kherson.
He spoke by videolink to leaders of the G20 nations who have gathered for a summit on the Indonesian island of Bali that is overshadowed by the war in Ukraine and worries over global inflation, food and energy security.
Zelenskyy said Ukraine would not allow Russian forces to regroup after their withdrawal from Kherson, adding that there would be more fighting until Ukraine reclaimed control of all of its occupied territory.
"I am convinced now is the time when the Russian destructive war must and can be stopped," he said, according to a copy of his speech reviewed by Reuters.
He said Kyiv would not compromise Ukraine's sovereignty, territory or independence, and also called for all Ukrainian prisoners to be released.
Ukrainian forces have been making advances in recent weeks against Russian troops in the east and south, last week recapturing the city of Kherson, the only regional capital Russia had captured since the February invasion.
On Monday Zelenskyy visited Kherson, which has become the biggest prize his troops have recaptured, vowing to press on until Ukraine reclaims control of all of its occupied territory.
Zelenskyy called on the G20 leaders at their summit, including US President Joe Biden and Chinese President Xi Jinping, to adopt a 10-point peace formula and end the war "justly and on the basis of the UN Charter and international law".
It was not immediately known if Russian Foreign Minister Sergei Lavrov, who headed the Russian delegation to the summit, remained in the room while the Ukrainian leader was speaking.
"If Russia opposes our peace formula, you will see that it only wants war," Zelenskyy said.
The Ukrainian leader also called for "radiation safety" around the Zaporizhzhia nuclear power plant, where fighting has been taking place, to be restored.
Leaders look to China to rein in Russia
British Prime Minister Rishi Sunak told the G20 that Putin's government would hear the chorus of global opposition to its actions. "Russia's actions put all of us at risk," he said at the summit in Bali.
He also confirmed a long-planned order for warships for Ukraine from BAE Systems, worth £4.2 billion (€4.79 billion).
French President Emmanuel Macron called on his Chinese counterpart to unite with France against the war in Ukraine. Speaking at the start of a bilateral meeting at the G20, he stressed that the "stability" of the world was also in China's "interest".
"Together with President Xi Jinping, we call for respect for the territorial integrity and sovereignty of Ukraine. The consequences of this conflict go beyond European borders: it is through close coordination between France and China that we will overcome them," Macron said on Twitter.
Kyiv has welcomed Chinese comments criticising threats to use nuclear weapons, after US President Joe Biden and Chinese President Xi Jinping met on Monday.
A readout of their meeting on China's foreign ministry website said "confrontation between major countries must be avoided".
Russian President Vladimir Putin has repeatedly suggested Russia could use nuclear weapons to defend its territorial integrity, interpreted in the West as an implicit threat to use them over lands Moscow claims to have annexed in Ukraine.
China has refrained from publicly criticising Russia for the invasion, but Zelenskyy welcomed Beijing's remarks, saying in an address late on Monday: "Everyone understands to whom these words are addressed."
G20 will condemn Russia for 'wreaking havoc', says US
The United States expects the G20 to condemn Russia's war in Ukraine and its impact on the global economy at the conclusion of the meeting in Bali, according to a senior US official.
Speaking anonymously, US officials have said President Biden will be "unapologetic" in his defence of Ukraine, and that "the G20 will make clear that Russia's war is wreaking havoc for people everywhere and for the global economy as a whole".
European Council President Charles Michel said there was an agreement among officials on a text communique on Monday evening, which he described as "positive".
In an address to his country late on Monday, Zelenskyy referred to the G20 as the G19, apparently declining to acknowledge Russia's membership. Ukraine is not a member.
Leaders of the Group of 20, which includes countries ranging from Brazil to India, Saudi Arabia and Germany and account for more than 80% of the world's gross domestic product, opened their summit with a plea by host Indonesia for unity and action to mend the global economy despite deep rifts over Ukraine.