WASHINGTON - US President Donald Trump's National Security Council spokesperson Michael Anton was planning to leave the administration, the White House said on Sunday.

The announcement came one day ahead of John Bolton, the former hawkish diplomat, is to take the post as Trump's third national security adviser on Monday.

"Everyday I got to work with Michael was a good day and he will be greatly missed," said White House Press Secretary Sarah Sanders in a statement released on Sunday.

The White House did not specify why or when Anton would leave.

Anton was brought into the council by Michael Flynn, Trump's first national security adviser, who pleaded guilty to lying to the Federal Bureau of Investigation last year over his contacts with Sergei Kislyak,former Russian ambassador to the United States.

Anton's departure was the latest in a series of staff removals in the Trump administration.

On March 22, the White House announced the departure of National Security Advisor H.R. McMaster, making room for Bolton, who is expected to add more momentum to the increasingly assertive US foreign policy.