U.S. President Donald Trump declared in a Sunday Truth Social post that British Prime Minister Keir Starmer will resign from his post.

Trump United Kingdom. He failed badly on two very important subjects- IMMIGRATION AND ENERGY (OPEN NORTH SEA OIL!). I wish him well! President DJT," Trump declared in the Truth Social post.

Starmer, the leader of the Labour Party, has not announced that he will resign the prime minister post, but whether to resign or battle it out in a leadership contest against Andy Burnham, a source said, according to the outlet.

The Associated Press reported that Burnham will be sworn in on Monday to serve as a House of Commons lawmaker after recently securing victory in a special election.

Reuters reported that Starmer asserted Friday that he will run if there is a leadership challenge: "If there ​is ​a ⁠contest ... then yes I will run, ​I will stand."

Starmer issued a post on X about Father's Day on Sunday.

"Being a dad is my greatest joy. Today, I’m thinking about my dad, and the father I am to my children because of him. Happy Father’s Day," he wrote.

The Associated Press and Reuters contributed to this report.