The United Nations is taking a historic step to open up the usually secret process of selecting the next secretary-general, giving all countries the chance to question candidates on issues such as how they would resist pressure from powerful countries, tackle sex abuse by U.N. peacekeepers, and improve efforts to achieve peace.

Montenegro's Foreign Minister Igor Luksic was the first of eight candidates to face members of the U.N. General Assembly on Tuesday.

The secretary-general is chosen by the 193-member assembly on the recommendation of the 15-member Security Council. This has meant the council's five permanent members have veto power over the candidates — and that would not change with Ban Ki-moon's successor.

But for the first time, nations have an opportunity to probe views of the candidates.