AFP - Japanese diplomat Yukiya Amano took the helm on Tuesday of the UN atomic watchdog, pledging a steady hand to steer the agency through the storm surrounding Iran's nuclear drive.

"This is the first day as director general of the IAEA (International Atomic Energy Agency) for me," the 62-year-old told reporters as he arrived for his first staff meeting on a cold, rainy day in the Austrian capital.

"As you can see, it is raining," Amano said. "But the situation surrounding the agency is stormy now. We have a lot of difficult issues and challenges, but I would like to do my best."

Amano, who succeeds the Egyptian diplomat Mohamed ElBaradei, is taking over at a particularly difficult time for the agency with a solution to a long-running stand-off with Iran apparently farther away than ever.

Last week, the watchdog's 35-member board passed a sternly-worded resolution against Tehran over its controversial nuclear programme, which after nearly seven years of intensive investigation the IAEA has been unable to confirm as exclusively peaceful as the Islamic republic claims.

In retaliation, Tehran said it planned to build 10 new uranium enrichment plants.

The Islamic Republic slammed the IAEA resolution as an "act of bullying" and has even begun to question the importance of the Non-Proliferation Treaty (NPT), something that is never done before.

The installation of Amano, who served as Japan's ambassador to the IAEA from August 2005 until his selection as director general in July 2009, marks a new era in the agency after ElBaradei's 12-year stint in charge.

ElBaradei came under frequent fire during his three terms as IAEA chief for being too soft on Iran and overstepping his mandate as head of a purely technical agency by making political statements.

Amano promised to be "impartial, reliable and professional as director general. I would like to get your support."

"I would like to address the global issues, that includes non-proliferation of nuclear weapons, enhancing nuclear security, addressing energy needs, providing good healthcare and water management among others," Amano said.

In Tokyo, Japanese Foreign Minister Katsuya Okada said he was "sincerely and profoundly pleased" Amano had become the first Asian head of the IAEA.

The watchdog "is faced with a variety of challenges including the nuclear issues in North Korea and Iran as well as the necessity to strengthen technical cooperation for nuclear energy in order to address global issues in fields such as medicine, food provision and the environment," Okada said.

In Vienna, where the IAEA has its headquarters, Austrian Foreign Minister Michael Spindelegger described Amano as an "experienced diplomat and expert in the areas of nuclear disarmament and the non-proliferation of weapons of mass destruction".

Spindelegger also thanked ElBaradei for "strengthening the IAEA and Vienna as a hub of international security dialogue with his steady hand, expert knowledge and clear-sighted view of the big picture."

The change in leadership at the IAEA came at a particularly challenging time, the Austrian minister said.

"Iran's latest announcement that it plans to build further enrichment plants deals a severe blow to our efforts to reach a negotiated solution," he said.

"Our hand remains outstretched, but the patience of the international community is wearing thin. Iran must not allow things to escalate further."