The World Bank chose Korean-American physician Jim Yong Kim as its next chief on Monday in a decision that surprised few despite the first-ever challenge to the US lock on the Bank's presidency.

The Bank's directors chose Kim, a 52-year-old US health expert and educator, over Nigerian Finance Minister Ngozi Okonjo-Iweala, who had argued that the huge lender needs reorientation under someone from the developing world.

Kim, currently president of the Ivy League university Dartmouth College, will succeed outgoing president Robert Zoellick, the former US diplomat who is departing in June at the end of his five-year term.

The Bank's directors expressed ‘deep appreciation’ to Kim, Okonjo-Iweala and a third candidate, Colombian economist Jose Antonio Ocampo, who pulled out of the race Friday.

"Their candidacies enriched the discussion of the role of the president and of the World Bank Group's future direction," the Bank said in a statement.

"The final nominees received support from different member countries, which reflected the high caliber of the candidates."

The US nomination of Kim, breaking the pattern of the 11 American bankers and diplomats who have come before him, had surprised many, as he was little known outside global health circles.

Some also criticized his lack of a background in development economics needed to run an institution heavily rooted in economic analysis.

But the South Korea-born, US-raised physician and anthropologist, with degrees from Harvard University, has a strong record in developing programs to fight diseases like HIV/AIDS and tuberculosis in poor countries.

He said after being nominated that he had the ability to work with economists and other specialists in running the Bank, which has a staff of 9,000 and a loan portfolio that hit $258 billion in 2011, including $43 billion in new loans and grants.

"I will come with an open mind and apply my medical and social-science training to take an evidence-based approach," he said, before embarking on a globe-spanning trip to convince other countries to back him.

"There's just no comparison between him and any of the prior World Bank presidents," said Mark Weisbrot of the Center for Economic and Policy Research in Washington, after Kim was chosen president.

"The others were political insiders; they spent most of their lives getting rich or becoming politically powerful, or worse. Kim, by contrast, has spent most of his life trying to improve the lives of poor people."

There had been little doubt about the Bank's choice of Kim. By a longstanding pact Washington has chosen the head of the World Bank while Europe has held control of who leads its sister institution, the International Monetary Fund.

On Friday Ocampo pulled out of the race, saying the decision would be made on politics and not merit. Okonjo-Iweala said the same earlier on Monday.

"You know this thing is not really being decided on merit," she told reporters in Abuja.

"It is voting with political weight and shares and therefore the United States will get it."

Even so, after earlier promising the Bank's board of executive directors would decide by ‘consensus’, there was no mention of the word in the announcement, suggesting that some directors held out for Okonjo-Iweala, who spent more than two decades working at the Bank.