A United Nations treaty banning governments from using children under the age of 18 in warfare went into effect Tuesday in an effort to reduce the number of child soldiers around the world.

Olara Ottunu, the Special Representative on Children and Armed Conflict, says in order for the measure to work, countries must simply do more than sign on to the protocol. The new measure must be taken to areas of the world engaged in warfare so that armed groups can be persuaded to stop the practice of using children to fight. He said, "This provides us with a new and very powerful tool for advocacy on the ground. We must take this treaty from New York, Geneva, Vienna, to the theatres of conflict and make them bite on the ground."

Mr. Ottunu says in order for this protocol to work, the U.N. must use all the means at its disposal to encourage its adoption. He says this includes "naming and shaming", or, focusing attention on parties who do not endorse it. International isolation and the denial of legitimacy for rebel fighters are other options the U.N. will consider.

Mr. Ottunu added that an upcoming speech by U.N. Secretary-General Kofi Annan to the Security Council will include a list of combatants who persist in this practice. Other punitive measures are also being considered by the U.N.