It's a message the UK has been doing its best to reinforce, with Mr Starmer expressing his "concrete" backing for Ukraine in a phone call on Friday and insisting "there can be no talks about Ukraine, without Ukraine".
That warm personal relationship is going to come under increasing pressure given the growing divergence of UK and US positions on the topics Mr Starmer will certainly want to discuss - Ukraine, the Middle East, trade tariffs and the Chagos deal for starters.
The White House does now seem to have accepted that Ukrainian President Volodymyr Zelenskyy will need to be at the table, with UK Foreign Secretary David Lammy telling reporters that US vice president JD Vance had agreed the Ukrainians will have to be part of any future deal.
On Friday, Mr Starmer reiterated the UK's commitment to Ukraine being on an "irreversible path to NATO as agreed by allies at the Washington Summit last year".
But it's also true that Mr Starmer has pledged the UK would "play its full part" in any peacekeeping operation in Ukraine in the future.
