Ukrainian President Volodymyr Zelenskiy says now is the time to push for peace after Russia's defeat in the southern city of Kherson.
At the same time, he said Ukraine would not allow Russian forces to regroup after their withdrawal from Kherson, and said there would be more fighting until Ukraine reclaims control of all of its occupied territory.
Zelenskiy made his remarks in a speech to a Group of 20 (G20) summit in Indonesia, where Russia's invasion of Ukraine was a key focus of discussion among leaders of the world's major economies.
A day earlier he shook hands with soldiers and waved to civilians during a visit to Kherson, where he said Ukraine had gathered evidence of at least 400 war crimes committed by Russian troops including killings and abductions.
"I am convinced now is the time when the Russian destructive war must and can be stopped," he said via video link on Tuesday to the summit on Bali, according to a copy of his speech reviewed by Reuters.
He called for Russia to withdraw all its forces from Ukraine and reaffirm Ukraine's territorial integrity, and said Kyiv would not compromise its sovereignty, territory or independence. He also called for all Ukrainian prisoners to be released.
"Please choose your path for leadership - and together we will surely implement the peace formula," he said.
Kyiv also welcomed Chinese comments criticising threats to use nuclear weapons, after US President Joe Biden and Chinese President Xi Jinping met on Monday.
The two leaders "underscored their opposition to the use or threat of use of nuclear weapons in Ukraine," the White House said in a readout of the meeting in Indonesia on the eve of the G20 summit.
A readout of the Biden-Xi meeting on China's foreign ministry website made no use of the word "nuclear" but said: "Conflicts and wars produce no winner ... and ... 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.
Xi and Putin have grown close in recent years, bound by their shared distrust of the West, and China has refrained from publicly criticising Russia for the invasion.
Moscow says it is waging a "special military operation" in Ukraine to rid it of nationalists and protect Russian-speaking communities. Ukraine and the West describe the Kremlin's actions as an unprovoked war of aggression.
Ukraine has repeatedly said it is ready for peace, but will not cede territory.
"Ukrainian servicemen accept no talks, no agreements or compromise decisions," Commander-in-Chief Valery Zaluzhny wrote on Telegram late on Monday.
Kherson city had been the only regional capital captured by Russia since the invasion in February and Putin had proclaimed it "eternally Russian" six weeks ago.
Olga Fedorova, an English teacher in Kherson throughout the occupation, said lack of electricity or mobile internet connection meant many were unaware of events until Ukrainian troops raised their flag in the main square on November 11.
"We couldn't believe, we still can't believe that our Ukrainian army is here," she said. "We have been waiting for them all this time, all this eight and a half months."
Residents in and around Kherson interviewed by Reuters have described killings and abductions.
Russia denies its troops target civilians or have committed atrocities.