The New York Times reported citing Brown's daughter that he had died from pancreatic cancer at his home in Rancho Santa Fe, California.
Brown was a nuclear physicist who led US efforts to modernise its defence system with weapons that included cruise missiles, stealth aircraft, and other weapons programmes.
This evening we are mourning the loss of former Secretary of Defense Harold Brown. https://t.co/M1m5khOtvk pic.twitter.com/Huk0saT2G8
— Acting SecDef Pat Shanahan (@DepSecDef) 6 января 2019 г.
— Jerry Hendrix (@JerryHendrixII) 6 января 2019 г.
— Tᴏm Mᴏᴏʀᴇ (@PaperMissiles) 6 января 2019 г.
READ MORE: US Doesn't Intend to Have Indefinite Military Presence in Syria — US Official
In the 1970s, Brown had been a delegate to the Strategic Arms Limitation Talks involving the United States and the Soviet Union.