"He likely will leave Thailand on Sunday but the United States has not yet been able to confirm his flight," a senior immigration police official told news agency AFP on condition of anonymity.
In a surprise breakthrough to the 10 year old case, John Mark Karr, 41, was arrested on Wednesday by Thai police working with US law enforcement officials.
He told reporters yesterday that the child’s death was accidental and that he was "in love" with the girl.
However, doubts have emerged about the authenticity of his confession; after his ex-wife told a US television station that they were together across the country on December 26, 1996, the day JonBenet's body was found in the basement of her home in Boulder, Colorado.
US authorities in the state of Colorado, who requested his arrest, said more work still needed to be done on the case.