The embassy said it had no specific information about the possible timing, targets or methods of the terrorist attacks. But it urged American citizens in Saudi Arabia to exercise caution and be aware when visiting commercial establishments and other areas frequented by Westerners.
"We have issued a warden message about our knowledge of ongoing operation planning for terrorist attacks in the kingdom and we have urged American citizens to maintain a high level of vigilance," U.S. Embassy spokeswoman Carol Kalin told The Associated Press over the telephone.
Neither the embassy nor the consulate planned to close, Kalin said.
An embassy statement also referred to previous attacks in which "housing compounds and other establishments where Westerners may be located" were targeted.
Since May 2003, Islamic militants have carried out numerous suicide bombings and kidnappings and have regularly battled security forces.
The attacks, which have tended to target Westerners, have been blamed on the al Qaeda terror group and allied militants.