It is the world's most important organization, yet remains one of its most dysfunctional.
This week a former United Nations employee described a pervasive culture of impunity inside the organization - one in which whistle-blowers are punished for exposing wrongdoing. James Wasserstrom, a veteran American diplomat, said he was fired from his job and detained by U.N. police - who searched his apartment and placed his picture on wanted posters - after he reported possible corruption among senior U.N. officials in Kosovo.
As Washington steps back in the world, a dynamic United Nations must step forward. So far, the U.N. of Ban Ki-moon has not been up to the task.
"It's supposed to be maintaining the ideals of human rights, the rule of law and anti-corruption," Wasserstrom said in an interview. "And it doesn't adhere to them on the inside."
The United Nations is under attack as well for its decision last month to pay no compensation to the families of 8,000 Haitians who died and 646,000 who fell ill from a 2010 cholera outbreak that experts believe Nepalese U.N. peacekeepers set off in the country.
The organization, though, remains a vital tool. On Thursday, President Barack Obama used a White House meeting with U.N. Secretary General Ban Ki-moon to pressure North Korea. Administration officials hope that punishing new U.N. economic sanctions , supported by China for the first time, will cause North Korea to end its saber rattling.
"It's important for North Korea, like every other country in the world," Obama said, "to observe the basic rules and norms that are set forth, including a wide variety of U.N. resolutions."
The United Nations has been, and will always be, an imperfect institution. Its greatest strength - and weakness - is its 193 member states. Getting a majority to agree on major issues, pass reform or refrain from political patronage can be maddening. Russia's shameful blocking of Security Council action against Syria, for example, has shown the continued limitations of that antiquated body.
But the United Nations is likely to grow more important in the years ahead as Washington's fiscal problems curtail U.S. overseas ambitions. Sadly, as the United Nations enters a potentially dangerous phase of peacekeeping missions, Ban's leadership is lacking.
The 68-year-old former South Korean foreign minister has highlighted the need to combat global warming, create sustainable development and increase the number of women in leadership positions. But he has failed to provide the dynamic leadership and reforms the institution desperately needs.
"It's a very mixed record," said a senior United Nations official, who spoke on condition of anonymity. "He spends a lot of time in Davos, the Arctic Circle or Monaco, and meanwhile there are critical issues - such as the future of peacekeeping - facing a real crisis."
To the alarm of some, the United Nations is returning to the ambitious peacekeeping operations of the 1990s - some of which ended disastrously.
The Security Council last month authorized the creation of a 3,000-soldier-strong U.N. "intervention brigade" in Congo, with an unprecedented mandate to fight with government troops against rebels, or on its own. An 11,000-troop United Nations peacekeeping mission is also expected to arrive in Mali as French forces wind down their battle against militants there. A mission in Somalia is possible as well.
"We're talking about a new era of big demands on peacekeeping," said Kieran Dwyer, spokesman for the U.N. Department of Peacekeeping Operations. "We are on the cusp."