U.S. President Donald Trump has announced the replacement of his National Security Adviser, Gen. Herbert McMaster, with former U.S. Ambassador to the UN, John Bolton.

Trump announced on his Twitter handle that McMaster would handover to Bolton on April 9.

“I am pleased to announce that, effective 4/9/18, @AmbJohnBolton will be my new National Security Advisor.

“I am very thankful for the service of General H.R. McMaster who has done an outstanding job & will always remain my friend.

“There will be an official contact handover on 4/9.”

However, McMaster said in a statement released by the White House that he was leaving the position following his retirement from the U.S. Army.

“After 34 years of service to our nation, I am requesting retirement from the U.S. Army effective this summer after which I will leave public service.

“Throughout my career it has been my greatest privilege to serve alongside extraordinary service members and dedicated civilians.

“I am thankful to President Donald J. Trump for the opportunity to serve him and our nation as national security advisor.

“I am grateful for the friendship and support of the members of the National Security Council who worked together to provide the President with the best options to protect and advance our national interests”.

President Donald Trump, right, speaks as Army Lt. Gen. H.R. McMaster, left, listens at Trump’s Mar-a-Lago estate in Palm Beach, Fla., Monday, Feb. 20, 2017, where Trump announced that McMaster will be the new national security adviser. (AP Photo/Susan Walsh)