Such as leaky pipes lined with asbestos, creaky air conditioning systems and an eerie locked room housing outdated electrical systems pulsing with so much energy that computers won't work on the floor below.

Some years ago part of the roof blew off the sleekly curved General Assembly building, landing, by good fortune, on some parked cars rather than a passing ambassador.

Inside the chamber where delegates from the 191 member states gather to discuss poverty, human rights, peace and security, even the ambassadors were not immune from danger.

"We had to replace the entire ceiling there because parts of the ceiling were falling down on delegates' heads," said Peter Wendeborn, one of the architects working on a six-year renovation plan for the UN complex due to start in 2007.

The United Nations has been working for years on a $1.2 billion Capital Master Plan for renovating its ageing headquarters on Manhattan's East River, completed in 1952.

Financing is not finalised since the United States declined to make an interest-free loan, instead offering it at 5.54 percent. Member states are still deciding what to do.

The United Nations has been inviting diplomats, US congressmen and media to take the "dirty" tour of the building as part of a campaign to secure the necessary funding.

Not everybody is convinced. Senator Jeff Sessions, a Republican from Alabama, urged the US Senate in April to slash the proposed loan by half, saying $1.2 billion was an "outrageous" sum by commercial standards.

"This renovation plan is far too expensive. Donald Trump told me ... he had offered to do the project for $500 million, yet UN Secretary General Kofi Annan did not seem interested," Sessions told the Senate, referring to real estate tycoon Trump who has built skyscrapers throughout New York.

SEEKING A TEMPORARY HOME

The plan has hit another snag with the refusal this year by the New York City Legislature -- partly antagonised by UN opposition to the war in Iraq -- to approve a plan to build a new 30-storey office in a park next door as a temporary home for the 3,400-plus people who work at the United Nations.

UN officials are seeking alternatives. Brooklyn, across the river, wants the business while other suggestions include a new tower at the World Trade Center site or even a moored cruise ship.

Meanwhile, Wendeborn wants to tell anybody who will listen that the architectural landmark which boasts the likes of Le Corbusier among its designers has not weathered well.

Peeling back the cover of an air conditioning unit in a conference room high in the domino-shaped skyscraper that houses the UN Secretariat, Wendeborn crouches and peers in.

"That powdery stuff in the wall, it's asbestos," he says, adding that 4,000 units around the UN building contain asbestos, now linked to cancer and other diseases.

"Whenever we want to put in a light fitting we have to bring in men in space suits," Wendeborn said of the asbestos problem in the building.

Three floors of the skyscraper house ancient air conditioners with giant snaking pipes, coated in asbestos and many crumbling, rusting or leaking.

"The equipment was designed to last 25 years. It's 30 years beyond its lifespan," Wendeborn said. "The equipment manufacturer is out of business so we can't even buy parts."

"They've asked us to give this back for their museum," he added, pointing to a control panel with antique dials that could come straight from a 1950s film set of a space ship.

Though it is on international territory, the United Nations signed treaties agreeing to abide by local US regulations, but Wendeborn said US authorities did not come in to check. With constant budget woes and no commercial pressure to keep up, the building has not been maintained.

The heating and cooling system is so erratic that employees often shiver or bake with no recourse except to open the windows. Unlike most modern office blocks the windows do open, but that's yet another headache for building managers worried about bomb attacks.

There are also no sprinklers, and the fire alarm system is so outdated controllers can pinpoint the source of an alarm only to within three floors in the 39 storey tower.

The buildings will be completely gutted internally and refitted, though the basic shell will remain as Wendeborn said it would be more expensive to tear it down brick by brick.

The UN complex draws some 800,000 tourists a year, with visitors paying up to $11.50 for tours in several languages.

Josephine Wanjiku, a guide from Kenya leading a recent tour, explained the UN's work to visitors from Wales, Mexico and California. Standing in front of a mural she said: "You see destruction, concentration camps, people fighting. Then the UN is founded and you see resurrection where families start to move on after the UN is founded."