The former ambassador was hired by longtime Biden foreign policy aide Anthony Blinken.
He served for five years — from 1990-1995 — on the National Security Council staff under Presidents George H.W. Bush and Bill Clinton. One position he had was a special assistant and senior director for Russia, Ukraine and Eurasia Affairs.
Burns also was State Department spokesman for several years during the Clinton administration and was US ambassador to Greece.
Under George W. Bush, he was US ambassador to NATO and later the third-highest ranking State Department official — the Under Secretary of State — before retiring from public service in 2008.
Burns announced earlier this month that he was supporting Biden’s presidential bid.