Former United Nations climate chief Christiana Figueres (C) speaks during a debate in the United Nations General Assembly between candidates vying to be the next UN Secretary General at UN headquarters in Manhattan, New York, US, July 12, 2016. [Photo/Agencies]

UNITED NATIONS - The first-ever "globally televised" debate on Tuesday kicked off at UN Headquarters in New York for 10 of the 12 candidates, who have announced their bid to become the next UN secretary-general, and they will take questions from diplomats and the public at large.

The debate, also known as the townhall meeting at the UN, started at around 6:30 pm EDT (2330 GMT) and it is expected to conclude at 9:00 pm (0200 Wednesday GMT) and available free from UNTV and Al Jazeera Media Network, producers of the broadcast.

Ten candidates to have confirmed participation, after drawing of lots, have been split into two groups to participate in discussions and answer questions, the president of the 193-member General Assembly, Mogens Lykketoft, said on Monday.

The first group consists of Vesna Pusic of Croatia, Antonio Guterres of Portugal, Susana Malcorra of Argentina, Vuk Jeremic of Serbia and Natalia Gherman of Moldova.

In the second group are Helen Clark of New Zealand, Danilo Turk of Slovenia, Christiana Figueres of Costa Rica, Igor Luksic of Montenegro and Irina Bokova Bulgaria.

Srgjan Kerim of the Former Yugoslav Republic of Macedonia and Slovakia's Miroslav Lajcak were unable to attend, Lykketoft said.

The televised meeting continued a series of "firsts" regarding the selection of the next UN chief to replace Ban Ki-moon, who retires on Dec 31 after two five-year terms.

The Tuesday event follows the landmark informal briefings that began in mid-April, kicking off the process to select the top UN official.

During those hearings, candidates went before the General Assembly to present their respective "vision statements" on the challenges and opportunities facing the UN and the next secretary-general, and answered questions from the audience.

These first-ever briefings were mandated by the UN General Assembly and are distinct from the townhall-style event taking place here Tuesday. They will continue to be held as further candidates are presented.

The next informal briefing will be held on July 14, when the most recently-nominated candidate, Christiana Figueres from Costa Rica, will take her turn.

On Monday, Lykketoft said UN secretaries-general have been chosen behind closed doors in the past.

"This time, we want to ensure all UN member states, and the entire world, have a chance to know who the candidates are, what their vision is and see how they perform," he said.

"The aim we are looking for is much broader participation in the general (UN) membership and the general public of the world in the selection of the next secretary general," the president said. "This is the town hall of the United Nations."

According to the UN Charter, "The secretary-general shall be appointed by the General Assembly upon the recommendation of the Security Council."

Previously this has resulted in the council secretly choosing a single candidate for recommendation to the General Assembly.

The current selection process was opened up in the name of transparency and so far nine of the 12 candidates have been publicly interviewed by members in the General Assembly.