He entered the Foreign Service in 1929 and served in Berlin, Montevideo, Mexico City, Istanbul, Ankara, Santo Domingo, Bogota and Paris, as well as Washington.
He retired from the Foreign Service in 1962, but was a State Department negotiator on the Panama Canal treaty the next year.
[4] While Ambassador to Haiti in 1961, Newbegin was recalled to Washington prior to the inauguration of dictator François Duvalier, in protest of his fraudulent election.
A Marine colonel stationed in Haiti once referred to Newbegin as an "extremely decisive and strong-willed Ambassador", a judgement echoed in other sources.
While ambassador, Newbegin instituted a French-language training programme among US government personnel there, and urged Americans to step up their contributions to Haitian charities.