Nato chief Mark Rutte wants members to agree to plan at summit later this month but UK remains cautious

Britain has still not committed to agreeing an increase in defence spending to 3.5% of GDP by the mid-2030s at the Nato summit later this month in line with a proposal from the alliance secretary general, Mark Rutte, defence sources said.

Though Rutte visited Downing St on Monday and the Nato chief expressed confidence in a speech in London afterwards that countries would sign up, senior insiders complained that Britain was still dragging its heels over the issue.

One accused No 10 of “having its head in the sand”, and said Britain had been caught out by the unexpected willingness of countries such as Italy, Belgium and Canada – traditionally laggards on defence spending – being willing to sign up.

Rutte’s proposal, devised in response to pressure from the US president, Donald Trump, is for Nato allies to agree to dramatically lift core military spending to 3.5% of GDP in the 2030s, with a further 1.5% on cyber and other defence-related budgets.