World Bank President Robert Zoellick said on Wednesday he will step down in June and Washington pledged to name a replacement candidate within weeks for a job that has always gone to an American.

The Obama administration said it would open the process to competition, marking the first time it has shown willingness to loosen its grip on the world's top development lender.

Zoellick took the reins at the Bank in 2007 after a staff revolt pushed out Paul Wolfowitz, and he moved quickly to return the institution's focus to alleviating poverty.

Developing countries have for years pressed for a greater voice in leading global financial institutions and are likely to stress the importance of a competitive process, but the US is still widely expected to retain its hold on the job.

"It is very important that we continue to have strong, effective leadership of this important institution, and in the coming weeks, we plan to put forward a candidate with experience and requisite qualities to take this institution forward," US Treasury Secretary Timothy Geithner said in a statement.

While Geithner called for an "open and expeditious process," analysts say Washington can ill afford to give up the post without risking US Congress cutting funding for the bank.

In an interview with Reuters, Zoellick said his decision to leave on June 30 at the end of his five-year term was his own and was not due to pressure from the Obama administration.

The former US chief trade negotiator and deputy secretary of state dismissed speculation he would join a Republican presidential campaign as "not true," saying only that he would decide what to do next once he leaves the World Bank.

"It really was my own decision," Zoellick said. "My personal sense is it's time to move on and I think once you feel that way you shouldn't stay."

Zoellick, who discussed the selection process with the board in a two-hour meeting on Wednesday, said the first step was for the board to call for nominations. "An open process is important," he said.  - Reuters