"We wish to advise you that a report of unknown credibility indicates the possibility of a terrorist attack at the Tunisia Mall in Berges du Lac on Sunday, December 20, 2015. We advise you to avoid the area," the US embassy in Tunis said.
There was no immediate comment from the Tunisian authorities.
Tunisia is grappling with a growing extremist threat that has seen several major attacks claimed by the Islamic State group this year targeting tourists and security forces.
