UN is an international organisation founded after World War II aims to provide a dialogue platform between countries, fortifying international corporation and preventing future wars. There are currently 193 members lead by five permanent members of the Security Council - US, Russia, UK, France, and China. The organization currently has six principal organs: General Assembly, Security Council, Economic and Social Council, Secretariat, International Court of Justice, and the Trusteeship Council.
Transition time: shortlist offers a contest of contrasts
Seoul's Ban Ki-moon is a key player in the race to replace UN leader Kofi Annan this year, writes Greg Torode
It's probably not the most powerful job in the world, and certainly not the best paid. Yet being secretary-general of the United Nations is often said to be the most difficult.
This time it looks like an Asian representative will end up in the hot seat - the first since veteran Myanmese (then Burma) diplomat U Thant got the nod 45 years ago. A handful of Asian candidates are being touted, led by South Korea's foreign minister, Ban Ki-moon.
Just consider the challenges facing whoever replaces Kofi Annan when he steps down at the end of this year after two turbulent five-year terms.
The pressure is on for far faster reform of the UN's bloated global bureaucracy. Then there are the political, social and diplomatic divisions across the post-September 11 world. An unwritten convention suggests the role is rotated regionally, meaning the Asia region is long overdue to be represented.
Just last week the 53-member African Group of UN members announced that they backed an Asian for the post.
In typical UN consensus fashion, however, nothing is easy. The US, backed by Australia, has said the best candidate should get the job, regardless of region. China has said it will back an Asian candidate. The views of China and the US will be vital in the months ahead as both hold veto power as permanent members of the UN Security Council.
Other unwritten rules also apply. Decades of lobbying by France means any successful candidate must speak French. A representative from a large country and/or a permanent Security Council can be generally ruled out. So can one-party states and pariah nations. Obviously, diplomatic skills and the ability to forge agreement across diverse nations cannot be under-estimated. But you don't necessarily have to be a UN insider. And, glancing down the list of former leaders, charisma has never been compulsory, either.
So far, just three Asian candidates have emerged - South Korea's Mr Ban, Thai Deputy Prime Minister Surakiart Sathirathai, and Sri Lankan diplomat Jayantha Dhanapala, a former UN under-secretary-general for disarmament affairs.
East Timor's foreign minister and Nobel Peace laureate Jose Ramos Horta is also being touted, although he has yet to officially throw his hat into the ring.
The prospect of the independence hero entering the race has highlighted just how bloody it could become.
Some regional papers have suggested Mr Ramos Horta is simply not 'Asian' enough. (He was born in East Timor to a Timorese mother and a Portuguese father.) Mention his name to a South Korean or a Thai diplomat and they respond with a heavy sigh and a roll of the eyes. 'East Timor ... too small by far' is the standard response, despite Mr Ramos Horta knowing all about the UN's fickle ways after a 25-year fight to win support for his independence struggle.
Mr Surakiart - who was the first cab off the Asian rank - is still to garner full Thai support. His candidacy has been promoted by the national vision of Thai Prime Minister Thaksin Shinawatra, who's now battling intensifying protests on Bangkok's streets. And at 48, Mr Surakiart must battle perceptions he's too inexperienced for the job.
Not that it's going to be a cakewalk for Mr Ban, aged 61. The US has yet to formally back him while China may not want a close US ally in the job, despite its ever-closer relationship with Seoul. Japan is also withholding formal support for the time being.
In his first interview since announcing his bid, Mr Ban said he'd already been lobbying China and other influential nations. He's describing himself as both a UN insider and outsider from a nation that sees itself as a 'child of the United Nations'.
'We think we're a model of many member states of the UN, one who's been able to realise all the important goals and ideals of the UN charter,' he said, outlining a record of peace and stability as well as development, prosperity and human rights and democracy.
After years of economic and democratic development, he says the time has come for his nation to putting something back. 'We're proud of what we've achieved and now Korea wants to play a greater role in the world community ... we have a lot to offer.'
Mr Ban also plays the politician, highlighting reform as a key plank of the UN agenda - a goal, no doubt, that will be warmly welcomed in Washington. 'Korea has been carrying out a series of wide and extensive reforms in all areas of our lives ... I've always been at the centre of innovation and reform,' he said.
'The most important agenda item at this time is the reform of the UN.'
Mr Ban has a regional reputation for balancing firmness with geniality - a diplomat's diplomat who's now fulfillng a life-long dream to represent his nation on the international stage.
He has played a key role in the now-stalled six-party talks to defuse North Korea's nuclear ambitions. He says the wider cause of unification on the Korean peninsula can be served by having a Korean in such a high-profile job.