When Trygve Lie stepped down from his job as the United Nations' first ever secretary-general, he warned his successor that he would be taking on "the most impossible job in the world". Ban Ki-moon, the new UN secretary-general, had good cause to recall those words when he took office at the beginning of 2007.

There is no shortage of alarming problems in his in-tray. Over the next year, he may well face crises over Iran and North Korea's nuclear ambitions. The Darfur conflict continues to make the UN look impotent. The organisation also has a substantial and risky mission going on in Lebanon. The war in Iraq is escalating and may spread to other parts of the Middle East. In the next few months the UN will have to agree on the final status of Kosovo - an issue that bitterly divides Russia and the western powers. And those are just the political problems. Many people are also looking to the UN for a lead on vexing environmental, social and economic problems - climate change, HIV/Aids and global poverty.