Pakistan, June 22 -- UK Prime Minister Keir Starmer is facing a career-defining decision: step down or fight a possible challenge from Labour Party rival Andy Burnham.

Starmer has publicly vowed to stay in office, but pressure is building as more and more Labour Party colleagues conclude that his time is up. Expectation is growing that he will announce a timetable for his resignation as soon as Monday. That's the day Burnham will be sworn in as a lawmaker in the House of Commons after winning a special election last week.

Business Secretary Peter Kyle said Sunday that Starmer is "making time to reflect on the political realities, challenges and opportunities that he finds himself in."

"I know he is a prime minister who always puts his ...