President Barack Obama announced the decision to the back Kim, who was born in South Korea but raised in Iowa, in a speech at the White House.
"It is time for a development professional to lead the world's largest development agency," Obama said flanked by Kim, Treasury Secretary Timothy Geithner and Secretary of State Hillary Clinton.
The United States has held the presidency since the bank's inception after World War Two.
However it faces an unprecedented challenge to its grip on the World Bank presidency, with emerging economies poised to nominate at least one candidate on Friday to set up the first contested bid for the top job at the global development lender.
African powers Angola, Nigeria and South Africa today endorsed the nomination of Nigerian Finance Minister Ngozi Okonjo-Iweala, a respected economist and diplomat.
Meanwhile, a spokeswoman for U.S. economist Jeffrey Sachs said he was withdrawing his nomination in support of Kim.