Amidst the introduction of multiparty politics, Poungui resigned from the PCT on 28 November 1990 and became the leader of a new party, the Union for Social Progress and Democracy (UPSD). At the end of the June–October 1997 civil war, in which PCT leader Denis Sassou Nguesso returned to power, Poungui, as a supporter of President Pascal Lissouba, fled into exile. He remained in exile until 2006.