New York, New York - President Volodymyr Zelensky accused Russia on Wednesday of plotting potentially catastrophic attacks on Ukrainian nuclear plants in a defiant UN address in which he denounced bids to impose peace from the outside.

Zelensky sought to rally support among world leaders at their annual gathering in New York as his concerns grow, weeks before a US election that could sharply shift the stance of Ukraine's main backer.

Speaking from the UN rostrum in a black polo jacket, Zelensky said that Ukrainian intelligence has found that Russia is scanning the country's nuclear infrastructure by satellite.

Russian President Vladimir Putin "does seem to be planning attacks on our nuclear power plants and the infrastructure, aiming to disconnect the plants from the power grid," Zelensky said.

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"Any critical incident in the energy system could lead to a nuclear disaster, a day like that must never come," Zelensky said.

"Moscow needs to understand this, and this depends in part on your determination to put pressure on the aggressor," he told the General Assembly.

Russia captured the giant Zaporizhzhia nuclear plant soon after its invasion of Ukraine in February 2022.

Russia, in recent weeks, has been pounding Ukraine's electricity grid in what Western and Ukrainian officials describe as an attempt to leave the country shivering during the winter.

Zelensky, on Thursday, will head to the White House to see President Joe Biden and present what he describes as a "victory plan" that shows a path forward for Ukraine.

In his UN address, Zelensky singled out China and Brazil as he questioned the "true interest" of countries that have been pressing Ukraine to negotiate with Russia.

Employing the language of the Global South, Zelensky said: "You will not boost your power at Ukraine's expense, and the world has already been through colonial wars and conspiracies of great powers at the expense of those who are small."

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"Ukrainians will never accept – will never accept – why anyone in the world believes that such a brutal colonial past, which suits no one today, can be imposed on Ukraine now," Zelensky said.

Chinese Foreign Minister Wang Yi told a Security Council session on Tuesday that diplomacy was the only solution.

Zelensky last year flew to the General Assembly in a dramatic first wartime appearance, and while he maintains star power, the political landscape has changed.

Donald Trump, running again for president, on Wednesday called Zelensky the "greatest salesman on Earth."

"Every time Zelensky comes to the United States, he walks away with $100 billion," Trump said, claiming, "We're stuck in that war unless I'm president."

The US has provided around $175 billion in both military and economic assistance to Ukraine since Russia invaded in February 2022, and Biden has ruled out sending troops.

Trump, in the past, has voiced admiration for Putin and, during his 2017-2021 presidency, was impeached for the first time over delaying aid to Ukraine to press Zelensky to dig up dirt on Biden.

Zelensky said he hoped to see Trump while in the US and explain that the war is more complicated.

Zelensky has sharply criticized Trump's running mate, JD Vance, who has said bluntly that he does not care about Ukraine and that the US should focus instead on confronting China.

"Let Mr. Vance read up on the history of the Second World War, when a country was forced to give part of its territory to one particular person," Zelensky told The New Yorker.

In Germany, the second-largest contributor of military aid to Ukraine, Chancellor Olaf Scholz is also facing pressure from parties opposed to support for Kyiv.

Britain has been among the most robust supporters of Ukraine. Foreign Secretary David Lammy told AFP that his government was committed to helping "to put Ukraine in the strongest possible position" as winter approaches.