WASHINGTON – World Bank President Robert Zoellick said Wednesday he is stepping down, raising the possibility that a non-American might be chosen for the first time to head the 187-nation lending organization.

Zoellick, 58, informed the board he will leave June 30 at the end of a five-year term, during which he led the bank’s response to the global financial crisis.

The board now begins looking for a new president under guidelines directors adopted in 2011 calling for an “open, merit-based and transparent selection” process.

That suggests a break from the informal agreement that dates to the bank’s founding almost 68 years ago, under which the bank’s president is an American and the head of its sister institution, the International Monetary Fund, is a European.

There is no guarantee that a non-American will be chosen to head the bank even though China is now the world’s second largest economy, and Beijing and other countries with growing economic clout have been exerting pressure for a change in the U.S.-European arrangement.

The IMF was supposed to follow the same open selection guidelines when it searched for a new managing director last year, but wound up again choosing a European, former French Finance Minister Christine Lagarde.

The World Bank is an international financial institution that provides loans to developing countries. The IMF helps countries when they encounter financial crises. Both institutions are based in Washington.

The decision to leave was Zoellick’s, according to an official familiar with the situation.

In a statement, Treasury Secretary Timothy Geithner praised Zoellick’s leadership at the World Bank and said the administration would put forward a candidate for the World Bank board to consider as his replacement.

Geithner’s comments did not indicate whether the administration would be willing to back a non-American for the top job at the World Bank.

But the United States controls the largest share of votes on the World Bank board, giving it significant say in who leads the institution.

Oxfam, an international aid agency often critical of the bank, said developing countries should play a major role in choosing a successor to Zoellick.

Secretary of State Hillary Rodham Clinton and former Treasury Secretary Lawrence Summers have been mentioned as possible successors to Zoellick, but Clinton said last June, “I do not have any interest and am not pursuing that position.”

Zoellick said he will stay focused on being bank president until June 30 and will continue to drive policies and programs at a heightened tempo.

Under Zoellick’s leadership, the bank provided more than $247 billion to help developing countries boost growth and overcome poverty.

Zoellick said he was “pleased that when the world needed the bank to step up, our shareholders responded with expanded resources and support for key reforms that made us quicker, more effective and more open.”