Donald Trump has accused China of attempting to "interfere" in the US midterm elections because they don't want him to win.
The US president did not offer any details to support the claim.
Mr Trump, who was chairing the UN Security Council for the first time, said: "They do not want me, or us, to win because I am the first president ever to challenge China on trade, and we are winning on trade.
"We are winning at every level.
"We don't want them to meddle or interfere in upcoming (elections)."
US officials have not immediately responded to requests for comment after Mr Trump's claims.
A representative from China who attended the meeting could be seen coughing into his hand and shrugging as the president spoke.
President Trump imposed tariffs on $200bn worth of Chinese goods on Monday, with Beijing accusing Washington of "economic intimidation".
Beijing's retaliatory tariffs on $60bn worth of US goods were due to go into effect soon after the US sanction.
Mr Trump's claim comes amid an ongoing special counsel investigation into whether his campaign team colluded with Russia in the 2016 US election.
The are concerns that the November elections could also be vulnerable.
With the midterms less than two months away, US intelligence officials have said they are not seeing the intensity of the Russian intervention registered in 2016.
But they added they are concerned about activity from Russia, China, Iran and North Korea.
1:15Mr Trump also used his moment chairing the Security Council meeting in New York to talk about nuclear proliferation, issuing a strong warning to nuclear-aspirant Iran.
He branded the country the "world's leading sponsor of terror" fuelling "conflict around the region and far beyond."
The president has withdrawn the US from the 2015 Iran nuclear deal, accusing the country of destabilising actions throughout the region and support for terrorist groups like Hezbollah in Lebanon.
Tough sanctions are due to kick in against Tehran in November, and Mr Trump warned there would be "severe consequences" for any nation that defied them.
Mr Trump told the UN General Assembly on Tuesday that Iran's "sow chaos, death and destruction", and does not respect its neighbours or borders or the sovereign rights of nations.
Despite his tough talk, Mr Trump told the Security Council on Wednesday that he could envision relations with Iran moving along a similar "trajectory" as ones with North Korea.
The president belittled the North Korean despot Kim Jong Un at the UN in 2017, dubbing him a "Rocket Man" before threatening to annihilate his country.
The two leaders met in a landmark summit in Singapore in June 2018.
Mr Trump touted the "wonderful relationship" he has with Mr Kim on Wednesday, and teased details that a second summit between the two men could be released soon.
The president also condemned violence in the ongoing bloody civil war in Syria, saying that the "butchery is enabled by Russia and Iran".
He also waded into thorny Middle East politics, endorsing the two-state solution to bring an end the decades-long conflict between Israel and the Palestinians.
The US president explicitly backed Israel, noting the moving of the US Embassy to Jerusalem and suggesting that he saw progress on the horizon for Middle East peace.
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Mr Trump's speech to the UN was met with ripples of laughter from world leaders when he opened with: "In less than two years my administration has accomplished more than almost any administration in the history of our country."
His speech put him at odds with the General Assembly as he pushed forward his "America First" ideology.
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