The US president called Ukraine's leader a "dictator" on Wednesday and later said Sir Keir and French President Emmanuel Macron, both of whom will visit the White House in the coming days, "haven't done anything" to end the war.
Sir Keir Starmer has urged Donald Trump to stand by Ukraine with a security guarantee as he warned a bad peace deal would be a "disaster for everyone".
:: Education secretary Bridget Phillipson, campaigner for global health and education Sarah Brown, and shadow defence secretary James Cartlidge will be discussing all the latest political stories in the UK and around the world on the Trevor Phillips on Sunday show on Sky News from 8.30am.
The prime minister is due to meet the US president for talks in Washington DC next week amid fragile relations between America and Europe after Mr Trump launched a verbal attack on President Volodymyr Zelenskyy.
Sir Keir also said the UK must increase its defence spending and play a bigger role in NATO.
