The embassy said in a statement it has information indicating that "a group of attackers is possibly in place and ready to strike targets inside Kampala in February or March."
One of the targets is the national museum, the statement said, warning US citizens to avoid that site and other crowded public places or events.
Ugandan police have issued many terror alerts over the past year, warning that the al-Qaida-linked Somali militants of al-Shabab may be plotting an attack similar to the assault last September on an upscale mall in the Kenyan capital. At least 67 people were killed in that attack.