A West Texas woman has been charged with attempting to buy a seven-week-old infant from the child's mother for 2,000 dollars - to be paid in instalments, police have said.

Marilu Munoz, 27, and the child's mother, Joana Delacruz Huerta, 29, were charged with the sale or purchase of an infant, a third-degree felony, police in Abilene said.

Officers said they found out about the alleged sale from an anonymous tip on Thursday morning.

Some of the scheduled payments had already occurred, police Sgt Lynn Beard said.

"It was a one-on-one kind of thing, just someone who wanted a baby," the officer added.

Police said Huerta admitted that she had been pregnant and told officers where she thought the baby might be. Police found the child unharmed at an Abilene residence.

Police said they did not know who the baby's biological father was or how the two women had initially crossed paths. Munoz's husband, an illegal immigrant whose name was not released, was placed on an immigration hold at the county jail.

The infant was taken into custody by Child Protective Service, authorities said.