The officials, grouped in the agencys board of governors, deadlocked after the leading candidate, Yukiya Amano, a Japanese official who is his countrys ambassador to the organization, fell one vote short of the two-thirds majority required for election in the vote at the agencys headquarters in Vienna.
Mr. Amano outpolled his South African counterpart, Abdul Samad Minty, in three rounds of voting on March 26 and an additional three rounds the following day, but never obtained the necessary margin for victory.
With 24 votes required, Mr. Amano took 23 yes votes in the initial poll on his candidacy, and in a later round received 22 affirmative votes with one abstention. In the final round, Mr. Minty garnered 15 yes votes with one abstention.
Taous Feroukhi, chairwoman of the board of governors, told reporters that the field was now open to new contenders in the race to succeed Mr. ElBaradei, whose third four-year term expires in November. Mr. ElBaradei, 66, has held the post since 1997, when he took over from Hans Blix of Sweden. The IAEA is the United Nations nuclear watchdog. The agency plays a central role in monitoring and investigating charges of illicit nuclear proliferation and promoting atomic energy for peaceful purposes.
The election comes as the Obama administration is seeking to coax Iran into talks over its contentious nuclear enrichment program and the IAEA itself is investigating whether Syria has sought to build a covert nuclear capability. New candidates will have a month to announce their intentions, followed by another election, probably in early May. Mr. Amano and Mr. Minty may also be nominated by their countries to run again, Ms. Feroukhi said.