The nation's 200,000 letter carriers are taking on another assignment this month as they make their appointed rounds: In addition to delivering mail and keeping an eye out for their elderly or sick patrons, they are looking for missing children.

The new Child Alert program is a cooperative venture of the U.S. Postal Service, the National Association of Letter Carriers and the National Center for Missing and Exploited Children. Carriers who walk or drive the nation's streets will be supplied with pictures and information about children who have disappeared from home.

The photos also will be posted on bulletin boards in post offices to help alert clerks and other inside workers to the problem.

Halline Overty, who is coordinating the program for the union, said that letter carriers are ideally suited to look for missing children because they are "on the streets six days a week, delivering mail at hours when many children are around."

Many of the missing children -- government estimates say they number about 1.5 million -- are runaways, but an unknown number are believed to have been kidnaped.

Some are taken at such a young age that they may not even be aware that they are "missing," program officials said. In some cases, older children go away with relatives or strangers who tell them that their mothers or fathers are dead.

Letter carriers who think they may have located missing children will report to their supervisors, who will call police or local authorities.

The child search program is an extension of something mail carriers have been doing for many years for sick or elderly people on their routes.

For the past 10 years letter carriers have been keeping an eye on those patrons as part of a Postal Service-instigated "alert" program. Postal employes watch for any accumulation of mail and often check to see if patrons are all right, officials said. Hundreds of people, some suffering from strokes, heart attacks or injuries -- have been saved through the alert program, officials said.