China and India are the "primary funders" of the ongoing Russian war in Ukraine by continuing to purchase Russian oil, US President Donald Trump said in his UN General Assembly address on Tuesday.
Trump also demanded that European allies immediately stop buying oil from Russia.
"They have to immediately cease all energy purchases from Russia. Otherwise we're all wasting a lot of time," Trump said of Europe in his address.
The Trump administration had earlier imposed an additional 25 per cent tariff on New Delhi as a penalty for its purchases of Russian oil, taking the total levies imposed on India by the US to 50 per cent, among the highest in the world.
India has called the tariffs imposed by the US "unjustified and unreasonable".
New Delhi said that, like any major economy, it will take all necessary measures to safeguard its national interests and economic security.
In his return to the UN General Assembly podium, Trump accused the UN of fostering an "assault" through migration on Western countries that he said were "going to hell."
"It's time to end the failed experiment of open borders," Trump said at the General Assembly.
"Your countries are going to hell," he said, also attacking London's Mayor Sadiq Khan, the first Muslim mayor of a Western capital.
In his address, Trump also launched a sarcasm-laden broadside against the United Nations, saying the institution does not help peace and mocking the quality of the headquarters building.
"The UN has such tremendous potential. I've always said it -- it has such tremendous, tremendous potential. But it's not even coming close to living up to it," Trump said.
The 79-year-old even complained about a broken escalator and teleprompter at the New York headquarters of the UN, which he has repeatedly targeted during both of his presidential terms.
"This is these are the two things I got from the United Nations, a bad escalator and a bad teleprompter," he added.
He likewise used the major forum to denounce efforts to reduce global warming, calling climate change concerns "the greatest con job ever perpetrated on the world."
"What is the purpose of the United Nations?" asked Trump.
"All they seem to do is write a really strongly worded letter," he said. "It's empty words, and empty words don't solve war"
On the sidelines of the UN summit, Trump met Ukrainian President Volodymyr Zelensky.
When asked if NATO countries should shoot down Russian aircraft entering their airspace, Trump replied, "Yes, I do."
His remarks follow recent incursions by Russian jets and drones that have unsettled Washington's NATO allies in Europe.
Trump's second term has opened with a blaze of nationalist policies curbing cooperation with the rest of the world.
He has moved to pull the United States out of the World Health Organization and the UN climate pact, severely curtailed US development assistance and wielded sanctions against foreign judges over rulings he sees as violating sovereignty.
Opening the annual summit, UN Secretary-General Antonio Guterres warned that aid cuts led by the United States were "wreaking havoc" in the world.
"What kind of world will we choose? A world of raw power -- or a world of laws?" Guterres said.
On Ukraine, Trump will meet President Volodymyr Zelensky for the second time since he sat down in Alaska with Russian President Vladimir Putin on August 15 -- a summit that broke Moscow's isolation in the West but yielded no breakthrough on Ukraine.
Despite Trump's insistence that he can broker a quick end to the war, Russia has not only kept up its barrage of attacks on Ukraine in the past month but rattled nerves with drone or air incursions in NATO members Poland, Estonia and Romania.
Trump said last week that Putin had "really let me down."
One of Trump's few other one-on-one meetings will be with Argentina's right-wing President Javier Milei, an ideological ally to whose government the United States is considering offering an economic lifeline.
Ahead of his visit to the UN district, swarming with heavily armed police and agents and crisscrossed with barricades and road closures, the US Secret Service said they had disrupted a "telecommunications-related" plot.
The Secret Service said it a weaponized farm of more than 100,000 cellphone SIM cards that was capable of blocking communications around the UN, and that it "nation-state threat actors" were involved.
(With inputs from PTI and AFP)