(AFP) - Ukrainian President Volodymyr Zelensky in a wartime trip to the United Nations on Tuesday urged the world to stand firm against Russia's "genocide," as he tried to convince skeptical developing nations they share a stake in Kyiv's victory.

Taking the rostrum of the UN General Assembly in his trademark military fatigues, Zelensky renewed an invitation for world leaders to join a "peace summit" to end the invasion.

"For the first time in modern history, we have the chance to end the aggression on the terms of the nation which was attacked," Zelensky said in a speech met with applause led by Western nations but many empty seats elsewhere.

"This is a real chance for every nation -- to ensure that aggression against your state, if it happens, God forbid, will end not because your land will be divided," he said, but with sovereignty upheld.

Zelensky lashed out at Russia for what Ukraine says is the deportation of thousands of children. The practice has led the International Criminal Court to issue a warrant for the arrest of President Vladimir Putin of Russia, which says it is taking war orphans into foster care.

"Those children in Russia are taught to hate Ukraine, and all ties with their families are broken," Zelensky said, as Russia's deputy ambassador to the United Nations sat without expression.

"This is clearly a genocide. When hatred is weaponized against one nation, it never stops there," he said.

He accused Russia of using both energy and food as a way to pressure the world, after Moscow ended a UN-backed agreement to let ships of grain sail out of Ukraine.

"The aggressor is weaponizing many other things, and those things are used not only against our country but against all of yours as well."

- Warning to Central Asians -

Zelensky warned that Russia's other neighbors were at risk.

"Russia has almost swallowed Belarus. It is obviously threatening Kazakhstan and the Baltic states," he said.

The leaders of Kazakhstan and the four other Central Asian former Soviet republics met at the United Nations with US President Joe Biden in a first-of-a-kind summit.

Biden told the leaders that the United States backed their "sovereignty, independence, territorial integrity."

"These principles matter more than ever, in my view," Biden said.

Biden in his own speech to the United Nations, with Zelensky looking on, warned that Putin was hoping the world will "grow weary" over Ukraine.

"But I ask you this: if we abandon the core principles (of the UN Charter) to appease an aggressor, can any member state in this body feel confident that they are protected? If we allow Ukraine to be carved up, is the independence of any nation secure?" Biden said.

"We must stand up to this naked aggression today to deter other would-be aggressors tomorrow."

Zelensky is also meeting leaders less dedicated to Ukraine's cause, including Brazil's President Luiz Inacio Lula da Silva, who has styled himself as a neutral mediator.

"Work needs to be done to create space for negotiations," Lula told the General Assembly.

Turkish President Recep Tayyip Erdogan, who will also meet Zelensky, said that the "war will have no winners and peace will have no losers."

"We will step up our efforts to end the war through diplomacy and dialogue on the basis of Ukraine's independence and territorial integrity," Erdogan said.

Russia has met overwhelming criticism at the General Assembly over its February 2022 invasion, but the focus on the war has also drawn criticism from developing countries who believe it has distracted the West, especially from other urgent priorities.

"It is a grave indictment of this international community that we can spend so much on war, but we cannot support action that needs to be taken to meet the most basic needs of billions of people," said South African President Cyril Ramaphosa, who also met Zelensky

- Dire climate crisis warnings -

Secretary-General Antonio Guterres has tried to keep a focus on development. He opened the General Assembly with a bleak speech highlighting the recent floods that killed thousands in Derna, Libya.

"Even as we speak now, bodies are washing ashore from the same Mediterranean Sea where billionaires sunbathe on their super yachts," Guterres said.

"Derna is a sad snapshot of the state of our world -- the flood of inequity, of injustice, of inability to confront the challenges in our midst."

In similarly dark language, Biden used his speech to highlight the flooding as well as wildfires in North America and Europe and drought in the Horn of Africa.

"Taken together these snapshots tell an urgent story of what awaits us if we fail to reduce our dependence on fossil fuels and begin to climate-proof our world," Biden said.

© Agence France-Presse