Analysts describe Mr Amano as a reserved technocrat
The man named as the new head of the International Atomic Energy Agency (IAEA), Japanese diplomat Yukiya Amano, has acknowledged he is stepping into the sensitive post in "stormy" times.
The veteran diplomat, who held senior arms control posts in Japan and was Tokyo's representative at the agency, was elected to be its new director general in July.
Taking up the role at the helm of the Vienna-based body, the 62-year-old pledged to be an "impartial, reliable and professional" leader.
"We have a lot of difficult issues and challenges, but I would like to do my best," Mr Amano said.
Among them is Iran's disputed nuclear programme. The transfer of power at the UN nuclear watchdog comes as tensions between the country and the IAEA became increasingly fraught.
In response to a sternly-worded resolution against the country - which insists its nuclear programme is peaceful in purpose - Tehran has just announced it plans to build 10 new uranium enrichment plants.
Mr Amano's approach to this kind of escalation, analysts say, will be to attempt to defuse and de-politicise it, in contrast to his sometimes outspoken predecessor, Mohamed ElBaradei.
Regarded as a reserved technocrat, he has underlined the importance of working within the agency's mandate and avoiding straying into the political sphere.
"The IAEA's basic function is not political negotiation but implementing already agreed safeguards," he said in February.
"Remarks by the director have political implications which, if made without properly assessing these implications, can be very dangerous."
Mr Amano graduated from the Tokyo University Faculty of Law and joined the Japanese Foreign Ministry in April 1972.
He held increasingly senior positions in the ministry, notably as director of the science division, director of the nuclear energy division and deputy director general for arms control and scientific affairs.
In 2002 he was appointed director general for arms control and scientific affairs and two years later he became director general of the disarmament, non-proliferation and science department.
His work has included postings at Japanese embassies in Washington, Brussels, Geneva and Vientiane, Laos.
He took part in arms control talks that produced the 1995 extension of the Non-Proliferation Treaty (NPT), the 1996 Comprehensive Test Ban Treaty and the verification protocol for the 2001 Biological Weapons Convention.
Iran's nuclear plans are high on the IAEA's agenda
Most recently Mr Amano has been Tokyo's representative to the UN nuclear agency.
He served as chairman of the IAEA's policy-making board of governors in 2005-06 when the agency and its director-general Mr ElBaradei were jointly awarded the Nobel Peace Prize.
Mr Amano accepted the prize on behalf of the agency.
He was narrowly elected as the agency's new head in July, backed by Western powers, in an election race which highlighted a deep divide between industrialised and developing nations on the IAEA's board.
As he formally took office, Mr Amano said he would address global issues such as non-proliferation, enhancing nuclear security and addressing energy needs but would also focus on the agency's role in fostering the use of nuclear energy for economic development and medicine.
He has also said he wants to improve communication between the IAEA inspectorate and its governors, and will manage the agency better.