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." This was reported by Qazaqyia.kz citing Associated Press.

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. But many in the military say that isn't fast enough.

"You have been unable, and the Treasury has been unwilling, to commit the resources that the nation needs to defend the country at this time of rising threats," Healey wrote in his resignation letter.

He said that the spending plan put forward by the Treasury would see defense spending rise to just 2.68% in 2030 after hitting 2.6% next year. Healey said that isn't enough with growing demands on defense and British military commitments, citing the Iran war, Russia's all-out invasion of Ukraine and threats from Moscow.

"I am now left with no other option than to submit my resignation," he said.

Healey has been U.K. defense secretary since the Labour Party government was elected in July 2024, and he's regarded as a capable and serious minister. He has played a key role in bolstering international support for Ukraine and assembling a multinational coalition to help guarantee security if a ceasefire is reached. Healey also has helped spearhead a maritime security force that would help keep the Strait of Hormuz open to shipping if the Iran war ends.

The United Kingdom and other NATO member nations have faced pressure from U.S. President Donald Trump to increase military spending. Trump has long questioned the value of the military alliance and complained that the United States provides security to European countries that don't pull their weight.

The U.K. military is also seeking to reverse years of decline in the face of an increasingly assertive Russia.