"China has been attempting to interfere in our upcoming 2018 election, coming up in November," said Trump.
China “doesn’t want me to win” the congressional elections, he said, without offering details of the alleged interference.
Trump is not up for re-election until 2020 but November's vote will decide whether his Republican Party can keep control of either house. All of the US House of Representatives (lower house) faces re-election along with about a third of the Senate, where Republicans currently hold a razor-thin, one-vote majority.
The shock revelation during a UN Security Council meeting aimed at tackling the proliferation of weapons of mass destruction drew an immediate rejection from China.
"We did not and will not interfere in any country's domestic affairs. We refuse to accept any unwarranted accusations against China," Chinese Foreign Minister Wang Yi told the Security Council.
Trump has triggered a trade war between the world’s two largest economies with the imposition of a new round of US tariffs this week on $200 billion in Chinese goods. China responded with duties of its own on $60 billion in US products.
"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," Trump said.
"We don't want them to meddle or interfere in our upcoming election," he added.
WATCH TRUMP'S FULL SPEECH AT THE UN SECURITY COUNCIL
No mention of Russian interference
US intelligence agencies have concluded that Russia interfered in the 2016 US presidential vote, casting a long shadow over Trump's presidency. In July at a summit in Helsinki, Trump said he accepted Russian President Vladimir Putin's denials of election meddling and the US president regularly describes the related investigations as a political witch hunt.
During his roughly 10-minute speech, Trump made no reference to Russian actions that allegedly helped bring him to power. An investigation by US Special Counsel Robert Mueller is looking into potential collusion between Moscow and the Trump campaign.
Trump also used Wednesday’s UN Security Council meeting to accuse Iran of helping spread weapons in the region and called on the international community to back US sanctions on Tehran.
(FRANCE 24 with REUTERS)