Earlier this week, Trump offered the position to Harward, following the resignation of Michael Flynn.
A senior White House official said that Harward turned the offer down due to conflicting financial and family commitments.
"Harward is conflicted between the call of duty and the obvious dysfunctionality," said an anonymous source close to the Vice Admiral, referring to the current working climate of the White House.
Harward is a friend of Secretary of Defense General James Mattis, and served as his deputy while Mattis led the US Central Command. Harward also served on the National Security Council during the administration of President George W. Bush.
The position is currently held by interim adviser Lieutenant General Keith Kellogg, a distinguished veteran in his own right. His name has been floated to hold the position permanently.
Another name that came up is General David Petraeus, former commander of ground forces in Iraq under President George W. Bush and CIA director for several years under President Barack Obama. Petraeus resigned in 2012 amid controversy when it was revealed that he had revealed classified information to his biographer who turned out to also be his mistress
