Topping the New Year's resolution list for new Secretary-General Ban Ki-Moon should be a good hard scrub of U.N. peacekeeping operations.

The United Nations now has more peacekeepers than ever before, deploying nearly 100,000 Blue Berets/Helmets (military, police and civilians) on 18 peacekeeping operations across four continents.

 That's more forces deployed abroad than any nation except the United States. In fact, if another large U.N. mission gets approved this year, U.N. deployments could actually top U.S. troop numbers in Iraq.

What's more, the peacekeeping budget consumes $5 billion of the U.N. Secretariat's $7 billion-a-year budget, and may rise to $7 billion next year. Washington pays the biggest single share (27 percent) of peacekeeping costs - not to mention other in-kind contributions.

But, while U.N. peacekeeping isn't cheap, it has a real place in promoting peace and stability around the world.

Sure, the 61 Security Council peacekeeping missions since 1948 have had a mixed record. But some have created much-needed diplomatic breathing room, providing both time and space for mediators and adversaries to conduct negotiations and resolve the differences that led to conflict.

In the United Nations' early days, peacekeepers deployed under its flag only as ceasefire monitors. But operations since then have often had much broader mandates. Now peacekeepers are frequently meant to serve as a buffer force, or to seize weapons, facilitate humanitarian assistance, protect refugees, maintain law and order - even to monitor human rights and elections.

For all the costs to Uncle Sam, having U.N. troops perform these tasks can actually be cheaper financially - and politically - for America than sending GIs off to handle the task, especially where U.S. interests are limited.

The problem is that the U.N. doesn't run these operations as efficiently or as effectively as it should. Some operations have long outlived their usefulness.  The one in the Western Sahara is already in its 15th year - and the warring parties, Morocco's government and the Polisario Front, still refuse to sign a 2001 agreement brokered by former Secretary of State James Baker. Peacekeeping cost: $45 million per year. Ka-ching! Some 43 U.N. observers still serve on the Indian-Pakistani "line of control" in Kashmir, established as the second U.N. mission in 1949. It's hard to see them having much effect on nuclear powers New Delhi or Islamabad resolving Kashmir.

The long-term presence of peacekeepers can also create a dangerous illusion of stability - even progress. The role of the U.N. mission in Lebanon (UNIFIL) before this summer's war between Israel and Hezbollah is instructive.

In 1978, the U.N. sent 2,000 Blue Berets to southern Lebanon to monitor Israel's withdrawal. UNIFIL certified Israel's pullback in 2000, but the Lebanese army never deployed south to fill the void left by the Israelis. Instead - while UNIFIL's presence provided a false sense of security - Hezbollah filled the military/political vacuum, a key step on the road to last summer's inconclusive conflict.

The "new and improved" UNIFIL, now 10,000 troops, may not prove any better. Sure, it's helped get humanitarian aid moving, but it's made no progress in disarming Hezbollah - or stopping arms flows from Syria and Iran, as the U.N. resolution called for.

Another tragic case of U.N. peacekeepers who failed because of a lack of political will behind them is, of course, the Rwanda genocide - which saw up to 1 million people slaughtered back in 1994.

To truly make a difference, peacekeeping operations need robust mandates that support Security Council resolutions - including the right (and the political support) to use lethal force to protect peacekeepers and civilians and to achieve mission objectives. Otherwise, the mission may be no better than putting a bandage on a cancer.

Secretary-General Ban also needs to end corruption in these programs: A U.N. audit in 2006 concluded that over a six-year period, $265 million of $1 billion in peacekeeping procurement contracting was subject to fraud, waste and abuse.

And he should ensure that peacekeepers - indeed, all U.N. staff - who commit crimes (such as the U.N. sexual abuse cases in the Congo) are tried and punished by their own governments. Unfortunately, this seldom happens.

Bottom line: U.N. peacekeepers can do important good work - when the missions have a clear purpose and strong Security Council mandate, supplement active diplomacy and are properly managed, policed and resourced.

Institutionalizing those conditions is no small challenge, Mr. Ban - better start resolving.