The UN's most powerful body, the Security Council, will meet later on Friday to hold another straw poll to gauge the popularity of a growing field of contenders to become the organisation's next secretary general.

Costa Rica's Rebeca Grynspan was the front-runner after last month's first informal vote, in which the council's 15 members, including the five with veto power, pass judgment in secret on the candidates.

Argentina's Rafael Grossi, the current head of the UN nuclear watchdog (IAEA), is also a candidate along with Chile's Michelle Bachelet, Ecuador's Maria Fernanda Espinosa, Guyana's Carolyn Rodrigues-Birkett, Uganda's Olara Otunnu and Senegal's Macky Sall.

After the first round concluded, Ecuador's Ivonne A-Baki threw her hat into the race to succeed António Guterres, who will complete his second five-year term on 31 December.

"While the first straw poll set the scene for the Secretary-General race, the second may give us some direction about where it is headed," said the International Crisis Group's Daniel Forti.