Starmer, 61, will attend NATO's 75th anniversary summit in the US capital on his debut foreign trip since becoming British leader last Friday.

He will reaffirm Britain's enduring support for the Western military alliance and Ukraine's fight against Russian aggression.

The visit kicks off a whirlwind of international diplomacy in Starmer's first two weeks in power, with the UK also hosting a European leaders' conference next week.

"It will be an opportunity for him to learn and get to know other leaders as much as to communicate any particular messages," foreign policy expert James Strong told AFP.

Britain's previous Conservative government was one of Ukraine's staunchest allies, providing money, weapons and troop training to help it repel Russia's invasion.

Starmer has pledged continued support for Kyiv under Labour, and is expected to reaffirm that message in person to Ukrainian President Volodymyr Zelensky at the NATO meeting.

Starmer's Defence Secretary John Healey has already visited Ukraine since last Thursday's election, and Foreign Secretary David Lammy has been visiting European NATO members.

Labour is committed to the alliance and wants to match the Conservatives' promise to raise defence spending to 2.5 percent of GDP, above the NATO target of two percent.

"We can expect lots of talk about 'business as usual'," added Strong, a lecturer at Queen Mary University of London.

While Starmer will stress continuity on the main foreign policy issues, he will also be keen to signal a reset in relations with allies that were soured by Brexit.

Labour has pledged closer cooperation with European neighbours, including on bilateral deals with France and Germany but also on agreements with the EU bloc as a whole.