WASHINGTON (Reuters) – U.S. President Donald Trump said on Friday he is considering four people to serve as his top aide on security, including acting national security adviser Keith Kellogg.

Kellogg, a retired general who was chief of staff of the White House National Security Council, stepped into the role after Michael Flynn resigned on Monday amid controversy over his contacts with Russia.

Trump had offered the job to retired Vice Admiral Robert Harward, who turned it down on Thursday.

Trump said in a post on Twitter he was still weighing other potential candidates for the White House job.

“General Keith Kellogg, who I have known for a long time, is very much in play for NSA – as are three others,” Trump said. He gave no other details about any of the contenders.

According to two sources familiar with Harward’s decision, the senior executive at Lockheed Martin declined the offer in part because he wanted to bring in his own team.

Trump has said that Flynn’s deputy, K.T. McFarland, could stay.

(Reporting by Susan Heavey; Editing by Frances Kerry)