In a statement on the eve of the start of the western group's two-day get-together in The Hague, Starmer said his government would aim to hit the pledge by 2035.

"We must navigate this era of radical uncertainty with agility, speed and a clear-eyed sense of the national interest to deliver security for working people and keep them safe," Starmer said.

"This is an opportunity to deepen our commitment to NATO and drive greater investment in the nation's wider security and resilience," he added.

The UK government said it expects NATO's 32 allies to agree to spend at least 3.5 percent of GDP on core military needs by 2035, and 1.5 on broader security-related items like cybersecurity and infrastructure.

The compromise deal aims to placate US President Donald Trump, who has repeatedly called for America's allies to dramatically ramp up defence spending.

NATO chief Mark Rutte has said that spending five percent on defence and security is essential to deter Russian aggression.

On Monday, he called the pledge a "quantum leap that is ambitious, historic and fundamental to securing our future".

Starmer had in February pledged to increase core UK defence spending to 2.5 percent of GDP by 2027, and three percent sometime in the early 2030s.