Japanese diplomat Yukiya Amano was elected director-general the United Nations nuclear watchdog on Thursday.
Looming challenges in the politically sensitive post include Iran's nuclear program, blocked investigations into alleged military nuclear activities in Iran and Syria, and North Korean nuclear tests.
Amano won the required two-thrids majority of International Atomic Energy Agency (IAEA) governing board members expressing a preference, with 23 votes and one abstention in the 35-nation meeting, defeating his South African rival.
But his triumph may be seen as hollow by many nations which wanted an IAEA leader with broad consensus backing raise questions about his authority in tackling rising threats to the global nuclear non-proliferation regime.
Amano defeated South Africa's Abdul Samad Minty in the last of four rounds of balloting by the UN atomic watchdog's executive body to prevail in his second run for the job after an inconclusive election in March.
But the fact that Amano, favored by industrialized nations, scraped through to victory by the bare minimum margin, without support of developing states, compounded a rich-poor split on the Board and may make it harder for him to lead the agency.