The changes were effected on Monday when Mr Kinyua, the Chief of Staff, took over the new duties after receiving his brief from the President.
He chaired the NSAC meeting held at Harambee House on Monday for the first time following the quiet changes by the President.
On Tuesday, Mr Kimemia confirmed the changes, saying, he will now be handling the duties of Secretary to the Cabinet while Mr Kinyua takes full charge of the expansive public service role, which also includes running of the top national security management team.
“It was clear from the time the President appointed me that I was only handling that particular docket on a transition basis. I am still serving the government as Secretary to the Cabinet,” Mr Kimemia told the Nation when reached for comment.
Under his role as the Secretary to the Cabinet, Mr Kimemia is in charge of the Cabinet office and keeping minutes of the Cabinet.
He also conveys Cabinet decisions to relevant authorities in government and may discharge other responsibilities as directed by the government.
Mr Kinyua is now one of the most powerful government officials.
Although it is not a constitutional or statutory institution, the NSAC is recognised as one of the most powerful organs in the security establishment, preparing briefings for discussion and approval by the National Security Council, which is chaired by the President.