The UN's International Organization for Migration (IOM) is set to choose its next director general on Monday.
The unusually tense contest is being fought by the US's Amy Pope, the IOM deputy director and her European boss Antonio Vitorino, the current IOM chief.
The 175 member states will vote by a secret ballot in closed-door meetings in Geneva.
Vitorino is only the second non-American to hold the top job since the agency was founded over 70 years ago. Pope, on the other hand, would be the first woman in charge if elected.
Who is the challenger Amy Pope?
Amy Pope is a US lawyer who has spent most of her career focused on migration issues, including within the administration of former US president Barack Obama.
The 49-year-old was also US President Joe Biden's senior advisor on migration after he took office in 2021. Prior to that, between 2015 and 2017 she was the deputy homeland security advisor.
Pope has also worked with the Chatham House international affairs think-tank in London. She began working at the IOM from September 2021.
Last year, after she announced her campaign, Pope took unpaid leave from IOM and focused on the fighting for her position as chief.
She said that while it is a "bit awkward" for her run against her boss, she said the agency needed a new vision.
"We're still kind of stuck in old ways of looking at migration," said Pope, calling for a broader focus on the impacts of climate change on migration.
Who is current UN migration chief Antonio Vitorino?
Antonio Vitorino has been running the UN's migration agency since 2018.
Before entering politics, the 66-year-old served as a judge at the Portuguese Constitutional Court for five years.
In the mid-1990s, he served as deputy prime minister and defense minister of Portugal.
He then went on to become the European Commissioner for Justice and Home Affairs.
Vitorino, who is close to UN Secretary General Antonio Gueterres, has touted the increase in the agency's annual budget as one of his major successes.
He called the current contest "unprecedented."
"We have never happened to have an incumbent director general that faces a competition with one of his deputy generals," Vitorino said. "Let's call it an innovation."
Vitornio expressed confidence in continuing as chief and said that he had the backing of Portugal as well as the "strong encouragement" of the EU.
Diplomats on facing pressure
Diplomats joked that they have been facing strong pressure from both candidates in recent weeks. Both have privately shown confidence in winning.
Voting could run into Tuesday depending on the number of rounds.
The IOM was founded in 1951 to handle the displacements in Europe following World War II, but only became a UN agency seven years ago.
Over 100 million people are currently facing forced displacement across the world. The IOM seeks to ensure humane and orderly migration and intervene in emergencies to help the vulnerable.
