The term of the current IAEA chief Mohamed ElBaradei, who has headed the agency since 1997, ends in November 2009. The 66-year-old ElBaradei, who together with the watchdog was awarded the Nobel Peace Prize in 2005, has signaled that he will step down when his term of office ends.
The 35-nation board will meet in a closed session. The two frontrunners are Japan's IAEA ambassador, Yukiya Amano, and South Africa's envoy, Abdul Samad Minty, both need to secure a two-thirds majority to win the vote.
Insiders say that Amano, whose candidacy is reported to be backed by the U.S. and some EU states, is the favorite for the four-year post over Minty, although neither is expected to garner the required two-thirds majority, which could mean the contest is thrown open to a new candidate.
The vote comes at a crucial time for the nuclear watchdog involved in stalled investigations in Iran and Syria and high-profile monitoring of North Korea's nuclear disarmament program.
In a recent report speech made to the IAEA board of governors on March 2 ElBaradei said that watchdog, charged with promoting the peaceful and safe use of nuclear technology, is continuing to monitor and verify the dismantling of North Korea's Yongbyon nuclear reactor, but said that despite numerous efforts there had been no progress in investigations into Iran's nuclear activity.