United Nations, United States: Portugal's former prime minister Antonio Guterres is poised to become the next secretary-general of the United Nations following a sixth straw poll by the Security Council, diplomats said Wednesday.

Russian Ambassador Vitaly Churkin emerged from the secret ballot along with the 14 other council ambassadors to declare that Guterres was the ‘clear favorite’ to succeed Ban Ki-moon as the world's diplomat-in-chief.

Churkin announced that a formal vote by the council will take place on Thursday to confirm the choice of Guterres, adding that he expected the selection to be ‘by acclamation.’

‘We wish Mister Guterres well in discharging his duties as the secretary general of the United Nations in the next five years,’ Churkin said.

During Wednesday's straw poll, veto-holders Britain, China, France, Russia and the United States used pink ballots to indicate for the first time whether they intended to block a candidate.

Guterres, who was the UN's refugee chief for 10 years, received 13 positive votes including four from the five veto-holding council members, and two ‘no opinion’ votes including one from a veto-holding member.

The 67-year-old, who served as prime minister from 1995 to 2002, had held the number-one spot in the previous five informal votes by the Security Council.

Once he is formally endorsed by the Security Council, the Socialist politician will be formally presented to the General Assembly for it to approve his candidacy.

There were 10 candidates in the race to become the next secretary-general including EU budget commissioner Kristalina Georgieva from Bulgaria who faced two vetos after entering the fray just last week.

Georgieva received eight negative votes including two from veto-holding members, five positive votes including two from the permanent council members and two ‘no opinion’. One of those was from a veto-holder.

The new secretary-general will begin work on January 1.