The US State Department has warned that "terrorists" could be about to attack US targets in the Arabian peninsula.
The peninsula comprises Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates, Oman and Yemen.
"In the past, such individuals have not distinguished between official and civilian targets. As always, we take this information seriously," the State Departmentstatement said.
The United States has already placed its embassies and other facilities in the region on heightened alert because of threats, the statement said.
Last month, US forces in the Gulf went on the highest state of alert, Threat Condition Delta, based on a broad but "credible" threat that US officials said was linked to exiled Saudi dissident Osama bin Laden.
A Pentagon spokesman would not comment on whether US forces in the region had now been placed on Threat Condition Delta.
US officials said they believed the threat warning was linked to bin Laden, who the United States has accused of masterminding the 1998 bombings of two US embassies in East Africa.
The threats were not tied to a specific time or place but seemed to focus on Saudi Arabia and Kuwait, US sources said.