If the United Nations fails to gain approvals to expand its headquarters in New York, will it be saying “Auf Wiedersehen”?

That’s “goodbye” in German, and at least one source close to the U.N. expansion project said talk has “been in the air” for several months about the possibility of using Bonn as a site for some U.N. offices should approval be withheld from plans to erect a 35-story office building near the U.N. campus during renovations of the Secretariat.

A number of sources familiar with the United Nations said transfer of the General Assembly and other organs of the main body to Bonn is highly unlikely. And a former U.N. ambassador, Richard Holbrooke, said that if the headquarters of the world body were moved from New York the organization “would collapse.”

Mr. Holbrooke was responding to questions about the United Nations’ relocating to Bonn even temporarily, as it proceeds with the proposed expansion of its footprint in Turtle Bay to accommodate more of the staff of the Secretariat.

Several persons following the drama over the United Nations’ bid to expand in New York said Bonn would be a logical choice for temporary relocation. The city, capital of free Germany during the Cold War, was left with several empty office buildings once the federal government moved to Berlin following Germany’s reunification.

Mr. Holbrooke said it would not be a problem for U.N. offices to move temporarily to Bonn.

“The Germans have always wanted to have an international organization in those empty buildings,” Mr. Holbrooke, who was a top adviser to Senator Kerry’s presidential campaign, said.

Bonn is already a U.N. city, host to 12 of the world body’s programs, ranging from the United Nations Volunteers Program to the Secretariat of the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas – which “covers all species of toothed whales in the Agreement area with the exception of the sperm whale.”

A total of 141 people work for the United Nations in Bonn, according to the U.N. spokesman’s office. U.N. staff in Geneva number 8,956; in Vienna, 3,211; in Nairobi, 1,672, and in Paris, 1,657.

Roughly 5,500 people work at the Secretariat in Manhattan, while an additional 1,800 non-Secretariat staff work elsewhere in the city, concentrated mostly in the area around U.N. Plaza.

Those numbers do not include the staffs of the 191 member nations’ U.N. missions.

The Web site of the German mission to the United Nations states: “The German Government is endeavoring to attract more United Nations bodies, as well as other international institutions, to Germany.”

While German officials have told The New York Sun that they are unaware of any current proposal to relocate the main offices of the main U.N. offices to Bonn, even temporarily, the spokesman for the German U.N. mission, Dirk Rotenberg, said: “If there is such a proposal we would consider it.”

Longtime U.N. insiders have said that over the years several attempts had been made at moving organizations such as the U.N. Development Program to Bonn. That program is one of the U.N. organizations currently housed in two auxiliary buildings across from the Secretariat, known as DC 1 and DC 2, for which the United Nations has long-term leases.

After the proposed renovation of the Secretariat, during which U.N. offices would be moved to the new, 35-story building, that swing space would be used to consolidate U.N. offices scattered around the city. If the organizations currently housed in DC 1 and DC 2 moved to Bonn, however, those structures would be left vacant – and could theoretically be used as swing and consolidation spaces in place of the proposed 35-story building.

The United Nations’ “founding fathers” put the world body in New York City for a reason, Mr. Holbrooke, who has long been considered a front-runner for appointment as secretary of state in a Democratic administration, said Thursday. “They understood completely that if the organization wasn’t anchored physically in the U.S., it wouldn’t have the U.S. support it needed to succeed,” Mr. Holbrooke said.

“The headquarters has to stay in New York,” he said.

The author of “Inside the Asylum: Why the United Nations and Old Europe Are Worse Than You Think,” Jed Babbin, offered a different view. Transferring the United Nations to Bonn, he said, “would be great.”

“The cost of it would be minuscule compared to the problems it would relieve the United States of – not the least of which is the presence of U.N. diplomats we have to maintain under surveillance and throw out of the U.S.,” he said. Mr. Babbin, a former deputy undersecretary of defense to the first President Bush, was referring to the Iranian U.N. “diplomats” who were caught allegedly casing sites in New York City to identify potential terrorist targets.

America’s deputy ambassador to the United Nations in the Reagan administration, Jose Sorzano, said a U.N. move to Bonn would make the Germans “ecstatic,” because “they would be very happy to take it away from Uncle Sam.” But he added: “One of the things that keeps the U.N. thriving is that it operates in this very sexy capital of the world.”

“The delegations that will have to go to Bonn instead of New York are going to be most unhappy,” Mr. Sorzano said. “It’s a nice city, but it doesn’t compare to the attractiveness of New York.”

U.N. officials, Mr. Sorzano said, who are happy with cushy posts in Manhattan would probably try to sabotage any attempt to move offices to Bonn.

While proponents of the U.N. expansion have expressed concern about the organizations moving abroad should its plans be denied, Mr. Sorzano said: “The threat to move anywhere else is not viable.”

The cost of transferring the organization overseas would be “staggering,” Mr. Sorzano said.

Moving to Bonn would also cause domestic unrest for foreign diplomats, he said. “Ministers are going to have huge fights with their wives,” he explained. “If they say, ‘Honey, we have to go to Bonn now for the General Assembly,’ they will have to deal with, ‘You mean I cannot go to Saks Fifth Avenue?’ “