UNITED NATIONS – As an increasing number of Americans call for an overhaul of Turtle Bay, Secretary-General Annan is expected to draw on a list of U.N. veteran insiders to fill a key post that was officially vacated yesterday.

Mr. Annan announced yesterday the retirement of the veteran British diplomat, Kieran Prendergast, who heads the United Nations’ department of political affairs. Mr. Prendergast, who for weeks has been known to be interested in stepping down, is expected to leave the post next month. He will remain on staff until the end of the year, a spokesman, Stephane Dujarric, said.

The political affairs department has become vulnerable to outside pressure following the events surrounding the war in Iraq and the increasing clash of sensibilities between the Bush administration and U.N. management. Washington is now expected to call on the United Nations to appoint someone from outside the organization, or at least an American ally.

For America, “this is a very important position,” a spokesman for the American U.N. Mission, Richard Grenell, told The New York Sun.

Italy wants to nominate its ambassador to the Organization for Economic Cooperation and Development, Francesco Olivieri, who is close to Prime Minister Berlusconi. Chile may try to nominate its U.N. ambassador, Heraldo Munoz, an acquaintance of Secretary of State Rice’s from Stanford University.

The United Nations is adamant that the post be filled with one of its own. Since Mr. Annan’s own mandate as secretary-general will only run for 18 months, “his priority is to find someone already thoroughly familiar with the work of the United Nations, who can ensure full continuity in the leadership of the department,” Mr. Dujarric said yesterday, adding that the appointment should be announced soon.

Several U.N. officials have been mentioned by insiders as top candidates, including current political affairs officials such as the Slovenian national Danilo Turk and the Nigerian-born Ibrahim Gambari, who heads the department’s African division. Another strong candidate is the deputy peacekeeping chief, Hedi Annabi, a U.N. veteran expected to retire around the time Mr. Annan’s term ends in December 2006.

What might help propel the candidacies of Mr. Gambari and Mr. Annabi, who is a Tunisian national, is the notion that the head of political affairs must now come from a “southern” nation, which refers not to countries in the Southern Hemisphere but rather to developing nations.

Since the early days of the United Nations, when a Soviet diplomat held the post, Britain had a virtual lock on the department of political affairs. Recently, however, Mr. Annan’s inner circle has become heavily British. Mark Malloch Brown, chief of staff since January, is considered the most influential official under Mr. Annan. Former Scotland Yard official David Veness was recently named security chief. The two joined yet another Briton close to Mr. Annan, top speechwriter and veteran Annan adviser Edward Mortimer.

The concept of creating an upper management balance between wealthy and developing nations is not necessarily of critical import in Washington, where the scandal-ridden United Nations has come under increasing scrutiny. Also, Americans have proved they have a lot of influence over the U.N. positions they consider important.

Mr. Prendergast, who served in the British foreign service before joining the United Nations in 1997, has been on a collision course with the Bush administration in the aftermath of the Iraq war. In recent months, he sought to become Mr. Annan’s Middle East envoy, but Washington blocked his nomination.

The Bush administration assumed Mr. Prendergast was responsible for a letter Mr. Annan wrote on the eve of the 2004 presidential election, urging Washington and its allies in Iraq to refrain from an assault on Fallujah – one reason to veto Mr. Prendergast’s nomination. The Bush administration regarded the letter, which was leaked to the press, as an attempt to sway the outcome of the American election.

Mr. Prendergast’s disappointment over the outcome of the envoy nomination, coupled with the upheaval throughout the organization, compelled him to leave. Mr. Dujarric said Mr. Annan announced the retirement “with real regret.” He said Mr. Prendergast will remain an employee and will spend next fall at Harvard University, writing a report on the United Nations’ role in mediation and conflict resolution.