The race for the next United Nations Secretary-General is officially underway, as several countries have already put forward their nominees.

However, the contest is already raising questions about tradition, regional rotation and gender balance at the world body.

Chile has nominated its former president Michelle Bachelet, with backing from Brazil and Mexico.

Argentina is supporting Rafael Grossi, the current director-general of the International Atomic Energy Agency, while Costa Rica has nominated Rebeca Grynspan, its former second vice-president.

In a surprise move, Burundi has nominated Senegal's former President Macky Sall, adding an African candidate to the race.

Tuliameni Kalomoh, who previously served as the Assistant Secretary-General for Political Affairs at the UN, says that although the rotation system is not a written law, it has guided UN leadership selections for decades.

The nomination of former Senegalese President Sall therefore overlooks the rotating system rule, Kalomoh argues, and is without official backing from his own government.

There is also growing international support for electing the first female UN secretary-general, which could strengthen the candidatures of leaders such as Michelle Bachelet or Rebeca Grynspan.

At the same time, Rafael Grossi remains a strong contender with support from the United States.

Once all nominations are finalised, the 15-member Security Council will begin a series of closed-door meetings and secret straw polls to narrow down the candidates.

The council will then recommend a nominee to the UN General Assembly, which will formally appoint the next Secretary-General.