U.K. Defense Secretary John Healey unexpectedly resigned on Thursday, saying the government isn't willing to spend enough on the military at a time of "rising threats." The resignation is another blow to embattled Prime Minister Keir Starmer, who is already facing demands from Labour colleagues to step down.

Healey told Starmer in a letter that the government's Defense Investment Plan falls "well short of what is required at this dangerous time." Publication of the plan has been delayed amid reports of disagreement between the defense ministry and the Treasury.

Starmer has pledged to boost U.K. defense spending to 2. 5% of gross domestic product by 2027 and 3% by 2034.