President Donald Trump’s deputy national security adviser, KT McFarland, has been asked to step down after just three months, US media say.
Ms McFarland, an ex-Fox News analyst, has been offered the role of ambassador to Singapore instead.
It comes days after Mr Trump removed his senior strategist Steve Bannon from the National Security Council (NSC).
The NSC advises the president on national security and foreign affairs.
Mr Bannon’s appointment in January raised fears that the circle of top advisers was being politicised.
Analysts say the latest moves show Mr Trump’s new national security adviser, Lt Gen HR McMaster, reshaping the NSC team appointed by his predecessor.
The previous national security adviser, Lt Gen Michael Flynn, was fired after just three weeks and three days in the job, after it emerged he had misled the vice-president over his conversations with Russia’s ambassador to the US.