The presumptive new prime minister will struggle to repair the U.S.-U.K. special relationship. Disagreements over China and defense spending will sustain.

British Prime Minister Keir Starmer announced on Monday his resignation as leader of the Labour Party, a decision that clears the way for the former mayor of Greater Manchester,…

The embattled British prime minister is widely expected to announce a plan for his exit just as his likely successor, Andy Burnham, arrives in Westminster.