The relationship between India and the US is facing one of its most significant challenges in decades, as the Trump administration doubles down on its demands that India stop buying Russian oil or face punitive tariffs.

The US president, Donald Trump, has refused to cut tariffs on Indian exports to the US, as he has for other countries, and on Monday said he would significantly raise them over its purchases of cheap Russian oil, which now account for one-third of its imported oil.

“They don’t care how many people in Ukraine are being killed by the Russian War Machine,” he said in a post to his Truth Social network, also accusing India of selling Russian oil “on the Open Market for big profits”. In a previous social media tirade last week, he said of Russia and India: “They can take their dead economies down together.”