President Donald Trump announced on Saturday that his chief of staff John Kelly would be leaving the position by the end of the year.

Trump made the announcement on the White House South Lawn before departing for the Navy vs. Army football game.

"John Kelly will be leaving at the end of the year. We will announce who will be taking John's place," Trump said, adding that there might be an interim chief of staff. "I appreciate his service very much."

Kelly's departure has been expected, according to sources within the White House.

His tenure has been marred by conflict since he took the position in the summer of last year. Reports have described disagreements between Kelly, the president and West Wing staff.

Recent clashes with first lady Melania Trump made his already tenuous position even more so, NBC News reported last month.

Kelly, a retired four-star Marine general, initially began his tenure in the Trump administration serving as the secretary of Homeland Security. He was tapped by Trump as chief of staff in July 2017 after his predecessor, Reince Priebus, was ousted following six months on the job.

During his time in the West Wing, speculation mounted that Kelly has been frustrated and exhausted by his role and Trump's temperament.

Among the leading candidates to replace him is Vice President Mike Pence’s chief of staff, Nick Ayers.

Outgoing House Speaker Paul Ryan, R-Wis., said in a statement that Kelly was departing "what is often a thankless job" and called him a "force for order."

“John Kelly is a patriot. Service to America is part of his DNA, and our country is better for his duty at the White House," Ryan said.

Trump also announced on Saturday that he had picked Gen. Mark Milley as his nominee to succeed Marine Gen. Joseph Dunford as chairman of the Joint Chiefs of Staff.

"Mark Milley, he is a great gentleman, he’s a great patriot, he’s a great soldier," Trump said Saturday.

On Friday, Trump announced he plans to nominate William Barr for attorney general.

Milley and Barr both must be confirmed by the Senate before assuming the positions.

If confirmed by the Senate, it would be Barr's second stint as head of the Justice Department. He served as attorney general from 1991 to 1993 under President George H.W. Bush.