In the Democratic Federal Yugoslavia's provisionary government that got formed on the basis of British-brokered Treaty of Vis and later the Belgrade Agreement, he was the deputy to the Foreign Affairs Minister. He then became one of the chief members of the secret Yugoslav diplomatic mission to Washington, negotiating the terms and scope of the American help to Yugoslavia. After returning home to the country that was in the meantime re-constituted as a Stalinist communist state called Federal People's Republic of Yugoslavia, he became deputy to Foreign Affairs Minister Stanoje Simić. In that role, Velebit negotiated with the Allies during the Trieste Crisis.