Washington: World Bank President Robert Zoellick said on Wednesday he plans to step down when his term ends on June 30, raising questions whether the United States will insist on holding on to a job that has always gone to an American.   

"I'm honoured to have led such a world class institution with so many talented and exceptional people," Zoellick said in a statement announcing his plans.    

Speculation has been rife in recent months over who might take the job when Zoellick departs. Possible U.S. candidates include Secretary of State Hillary Clinton and former White House economic adviser Larry Summers.   

Zoellick, a Republican, would potentially be a strong candidate for a senior position if a Republican candidate takes the White House in presidential elections in November.