The International Atomic Energy Agency (IAEA) says it aims to appoint a new director-general in October following the death of its previous head, Yukiya Amano, two weeks ago.
The Vienna-based UN nuclear watchdog said following a meeting of its board of governors on August 1 that member states could submit nominations until September 5.
The board "expects to appoint a director general in October 2019 and, in any case, envisages that the person appointed will assume office no later than 1 January 2020," it said in a statement.
The race to succeed Amano comes amid heightened international tensions over Iran's nuclear program.
Romanian diplomat Cornel Feruta, 43, is to head the agency in the interim until a permanent successor to Amano, who died at the age of 72 of an unspecified cause, is agreed upon.
The Japanese diplomat had held the position of IAEA director-general since 2009, steering the UN agency through a period of intense diplomacy over Iran's nuclear program.
Amano oversaw the 2015 signing of a landmark nuclear agreement between Iran and six major powers -- Britain, China, France, Germany, Russia and the United States -- which provided Iran with relief from sanctions in return for curbs on its nuclear program.
But the United States withdrew from the agreement last year and reimposed economically crippling sanctions in many sectors, including the crucial oil and financial industries.
The Western European signatories have tried to salvage the accord, but Iran complained that the process was too slow and amassed more than the permitted amount of low-enriched uranium.