The 60-year old Harward was the leading candidate to replace Gen. Michael Flynn, who resigned on Monday, after misleading Vice President Mike Pence about whether he discussed sanctions with the Russian ambassador before the inauguration.
Harward most recently served as the deputy commander of U.S. Central Command under Gen. James Mattis, the just-confirmed Secretary of Defense. He cited his family as the reason for declining the job, the senior Trump administration official said.
"I was humbled and honored," Harward said, adding that the position “takes 24 hours a day of focus... It's a tough sacrifice" and after 40 years of military service, he was not ready to come back from retirement.
Other names under consideration as a possible replacement for Flynn, include retired Gen. David Petraeus, former Ambassador Bob Kimmitt, and retired Gen. Keith Kellogg, who is currently serving as the acting national security advisor.
"I have somebody that I think will be outstanding for the position," President Trump said Thursday at a White House press conference.