On Friday, Colombia's Jose Antonio Ocampo pulled out of the race, calling the selection process a "political exercise".

Either Mrs Okonjo-Iweala or Dr Kim will replace Robert Zoellick, who has run the World Bank since 2007.

By convention, the US has always held the top job at the World Bank since it was founded in 1944.

The top job of its sister organisation, the International Monetary Fund, has also always gone to a European but there has been much pressure from emerging economies to open the processes of both organisations to competition.

"It's no longer in the smoke-filled rooms of Europe and the United States that the spoils are shared," South Africa's finance minister Pravin Gordhan said on Monday.

But he conceded that it was likely the "established powers" would make the final decision when the 25-member World Bank board meets to vote.

European countries are likely to support the US bid as has happened in the past. Europe and Japan together have 54% of the votes to appoint the bank's president.

The next president of the World Bank will oversee a staff of 9,000 economists and development experts and a loan portfolio that hit $258bn (£163bn) last year.