Sources close to the situation told CBS News that Harward and the administration had a dispute over staffing the security council.
Harward demanded his own team, and the White House resisted, they added.
Trump told Deputy National Security Adviser K.T. McFarland that she could retain her post, even after the ouster of National Security Adviser Michael Flynn. Harward refused to keep McFarland as his deputy, and after a day of negotiations over this and other staffing matters, Harward declined to serve as Flynn’s replacement.
Harward, a 60-year-old former navy officer, served as deputy commander of US Central Command under now-Defence Secretary James Mattis.
He previously served as deputy commanding general for operations of Joint Special Operations Command at Fort Bragg in North Carolina.
Harward has also commanded troops in both Iraq and Afghanistan for six years after the September 2001 attacks. Under former President George W. Bush, he served on the National Security Council as director of strategy and policy for the office of combating terrorism.
Flynn resigned from the post amid questions about his contacts with Russian officials, CBS News said.
Law enforcement sources confirmed earlier this week that Federal Bureau of Investigation agents had interviewed Flynn last month.
According to the Defence Intelligence Agency, Flynn’s security clearance has been suspended as investigators look into his ties to Russian officials.