The contest to replace António Guterres as U.N. secretary general has been jolted by last-minute entrants and deep divisions among members of the Security Council.

© Angelina Katsanis for The New York Times

Lana Nusseibeh, one of the Gulf nation’s top diplomats, has led the effort to deny her country’s role in Sudan. Now it’s complicating her bid to become secretary general of the United Nations.

© Eric Lee/Reuters