With just five days to go for nations to put forward nominees to lead the World Bank, there are few signs the United States has finalized its choice to lead the global development lender.

The United States has held the presidency of the Bank since its founding after World War Two, while a European has always led its sister institution - the International Monetary Fund.

But Washington has yet to publicly identify a candidate and some observers think the delay could signal that the White House is having a hard time convincing possible candidates to take the job. The White House and Treasury Department have declined to comment.

Sources with knowledge of the administration's thinking say the hope was to convince a woman to enter the race to replace Robert Zoellick, who has said he will step down when his term expires at the end of June.

Naming a woman could go some way to address calls from emerging-market nations for a change in the status quo. A woman has never led the bank.

Two sources said Susan Rice, the U.S. ambassador to the United Nations, was a leading contender. However, it is not clear she wants the job. Rice's name often surfaces as a possible candidate to succeed Hillary Clinton as secretary of state.

When asked last week how she would help South Sudan if she was president of the World Bank, Rice replied: Ridiculously hypothetical.

Senator John Kerry and PepsiCo's Indian-born CEO Indra Nooyi had also made an Obama administration short list, according to a source, although Kerry has publicly ruled out the job and another source said Nooyi was no longer in contention.

Another short-list member, Lawrence Summers, a former adviser to President Barack Obama and a one-time Treasury secretary, has declined to comment. He told Reuters he would leave the selection process to the officials in charge of it.

LEAVING THE DOOR OPEN

The delay in identifying a U.S. nominee could leave the door open to a dark-horse candidate from the United States. It has also given other nations time to consider their own nominees.

It wouldn't be the first time in history that the White House had to scramble a bit, said Whitney Debevoise, a former director to the World Bank board.

I think they have lost the opportunity to put a name out there early and make it uncontested, he added. Usually ... if the U.S. puts a name out there, then nobody else wants to put their name up because they know they don't have a chance.

Emerging and developing countries have been pushing to have more say at both the World Bank and IMF, and have said the decision on Zoellick's successor should be merit-based.

Developing and emerging market economies are currently in consultations on putting forward names of non-U.S. candidates. The dilemma for developing regions, however, is finding candidates willing to come forward in a race in which the outcome is felt to be pre-ordained.

Indeed, the two most talked about names among developing countries are former World Bank Managing Director Ngozi Okonjo-Iweala, now Nigeria's finance minister, and Trevor Manuel, the South African national planning minister. Former Indonesian finance minister and current World Bank Managing Director Sri Mulyani Indrawati, and Mexico's central bank governor Agustin Carstens have ruled themselves out.

World Bank board sources said there were also talks under way about possibly appointing a candidate from a developing or emerging economy to head the Bank's private-sector lender, the International Finance Corp. IFC CEOs have mainly been European.

The World Bank's 24-member board, which represents all of the institution's 187 member countries, has set a deadline for Friday for nominations to lead the Bank, and has said it would decide on the next president within a month.

ONE MAN RACE

U.S. economist Jeffrey Sachs, a professor at Columbia University, is the only formal candidate to have emerged so far. He has been formally nominated by Bhutan and a cluster of developing countries including East Timor, Jordan, Kenya, Namibia and Malaysia.

Jeffrey Sachs is a good economist and a very good candidate, but we expect to see the rest of the names and what follows in the process, Mexican Finance Minister Jose Antonio Meade said on Sunday.

Last week, 27 lawmakers wrote to President Barack Obama to strongly encourage him to nominate Sachs. Sachs, whose self-proclaimed candidacy aims to challenge what he sees as a history of political appointments by the White House, acknowledges he lacks the Obama administration's support.

They're not talking to me, he told Reuters.

With his early nomination, Sachs has had a head start in lobbying for support among developing countries where he has a proven track record on issues such as education, health, climate change and fighting poverty.

I have spoken with at least a couple of dozen leaders around the world in the last week and believe I have strong worldwide support in every region of the developing countries, and a lot of support in Europe as well, Sachs said.

For the European countries, they are not surprisingly saying that they are overwhelmingly likely to defer to the U.S. nominee and that they are waiting for that, he added.

Sachs said while the United States was still likely to determine who gets the job, a desire among developing countries to end tradition suggested that was not a sure bet.

I don't think it is automatic because of feelings that this is an important institution and an important moment, and I don't think the U.S. has simply the green light to choose anybody.

Officials argued that it is important for the United States to retain the presidency of the bank, otherwise political support and funding for the institution could erode, given that Congress is focused on budget cutting.

The United States is the World Bank's largest donor.

(This version of the story has been corrected to fix the date in the dateline)

(Reporting by Lesley Wroughton; Editing by David Brunnstrom)