VIENNA (Reuters) - The U.N. nuclear watchdog’s chief, Yukiya Amano, will secure a third term in office since his most likely challenger has chosen not to run against him, according to diplomats who follow the Vienna-based agency.

International Atomic Energy Agency (IAEA) Director General Yukiya Amano smiles as he waits for a board of governors meeting to begin at the IAEA headquarters in Vienna, Austria June 6, 2016. REUTERS/Heinz-Peter Bader

Amano, a 69-year-old career diplomat from Japan, has headed the International Atomic Energy Agency (IAEA) since 2009. He said in September he would seek to stay on, emphasizing the importance of continuity in policing Iran’s nuclear deal with major powers, among other issues.

“There will be no other candidate,” a Western diplomat said on condition of anonymity, adding that Amano enjoys broad support. “It’s a done deal.”

Amano was expected to be challenged by Argentine diplomat Rafael Grossi, a Vienna veteran who recently chaired the Nuclear Suppliers Group, an export control body. But with an end-of-year deadline for bids approaching, he had bowed out, diplomats said.

Argentina has decided to wait until the end of what would be Amano’s third term, in 2021, to put Grossi forward as a candidate, another diplomat familiar with the matter said.

Grossi was not immediately available for comment.

Amano was first elected by the IAEA’s 35-nation Board of Governors with the support of Western countries looking for a more pliant successor to Mohamed ElBaradei of Egypt, who frequently clashed with U.S. officials over Iran.

ElBaradei and the IAEA were awarded the Nobel Peace Prize in 2005, two years after the U.S.-led invasion of Iraq. Officials from the George W. Bush administration, which was in power at the time, accused ElBaradei of being too lenient towards Iran.

Amano, a more low-key figure known for his guarded statements, regularly emphasizes that the IAEA’s work is technical, striking a deliberate contrast with ElBaradei’s more political style.

Diplomats say he has established himself as a competent leader through episodes like the 2011 Fukushima Daiichi nuclear disaster in Japan - a tough test for the IAEA, which is tasked both with nuclear safety and with promoting nuclear energy.

He has also overseen inspections of Iran’s nuclear program, a role that continues under the landmark deal with major powers reached last year, which restricts Iran’s atomic activities in exchange for the lifting of sanctions against it.

With U.S. President-elect Donald Trump - a vocal critic of the deal - due to take office next month and his future policy towards Iran uncertain, many see the need for a safe pair of hands.

“Amano does not generate any enthusiasm but is seen as a figure that does not rock the boat,” said one diplomat who is critical of him.

Amano’s second four-year term runs until November. The Board of Governors is due to meet during the year to elect the next director general.