WASHINGTON (AP) _ As families of kidnapped and murdered children watched, President Clinton today signed an order that will set aside an area in all federal buildings for the posting of missing children notices.

``This is more than a bulletin board, this is a helping hand,'' said Claudine Ryce, the mother of 10-year-old Jimmy Ryce, who was kidnapped in Miami and murdered by a stranger last year.

When a child is abducted, she said, ``the only lead we have is the child's face.''

The president issued the executive order two days after the body of Amber Hagerman was found in Arlington, Texas, floating face-down in a creek, her throat cut. The 9-year-old was dragged screaming off her bicycle last Saturday afternoon by a man in a pickup.

``For every parent, one of the most horrible things imaginable is the disappearance of a child,'' said Clinton. ``We must do whatever we can to help parents in these situations find their children.''

He urged people to ``look twice at the photos of missing children you see in the mail, on your milk cartons, and now, in federal buildings across the country.''

About 300 kidnappings occur each year where the suspect is not a family member, according to the National Center for Missing and Exploited Children funded by the Justice Department. A far larger number, 350,000, involve family abductions.

Attorney General Janet Reno said the first 24 to 48 hours are critical in a kidnapping and she said an effort is under way to tie 16,000 police departments into a notification system where reports of missing children will be highlighted.

After Jimmy Ryce's disappearance on Sept. 11, 1995, Mrs. Ryce said, she and her husband posted his picture in public buildings.

``We even had Jimmy's picture taken down,'' she said. ``We were told it wasn't authorized.''

Reno said the federal building displays will not be mixed in with other notices, such as wanted posters and job openings. Clinton's executive order requires that a space be set aside just for missing children.

Don Ryce, the boy's father, said the president's order resulted not just from the drive spearheaded by parents but that all the people of south Florida are involved.

Other parents at the signing were:

_Colleen Nick, mother of 9-year-old Morgan Nick, kidnapped by a stranger in a ballpark in Alma, Ark., last June.

_Linda Koerner, paternal grandmother of Adam Croote, who was taken at age 6 by his maternal grandparents from Dormansville, N.Y., but recovered three years later.

_And Marc Klaas, father of 12-year-old Polly Klaas, who was taken from a slumber party in her bedroom in Petaluma, Calif., on Oct. 1, 1993. She was strangled and her body was dumped beside a highway.