The United States and Australia have warned their citizens living in Indonesia of a possible terrorist attack somewhere in the country on Sunday.

A letter sent to American citizens by the U.S. Embassy in Jakarta said "terrorists continue to plan attacks against Westerners and Western interests in Indonesia."

The letter, sent Friday, went on to say that "recent reports suggest that Sunday, April 2, 2006, could be one potential date for an attack."

The statement said locations that are frequented by foreigners or "identifiably American" were likely targets, although it provided no specifics.

Indonesia has experienced several terrorist attacks in recent years blamed on the Al Qaeda-linked Islamic extremist group Jemaah Islamiyah.

The group has been implicated in two strikes on the resort island of Bali that killed more than 220 people, including 88 Australian tourists, and the 2003 car bombing of the J.W. Marriott Hotel in Jakarta.

The U.S. statement echoed a similar warning issued by Australia in recent days.

Australia's Department of Foreign Affairs and Trade updated its travel advice on Saturday to say it had received a stream of reports indicating that terrorists were in the advanced stages of planning attacks against Western interests in Indonesia.

"These reports include information about potentially heightened risk of attack on particular dates," the department said on its Web site, citing Sunday, April 2.

That date is the first anniversary of a helicopter crash that killed nine Australian military personnel who were flying a medical relief mission on the Indonesian island of Nias days after a major earthquake.

Australian Foreign Minister Alexander Downer said an Australian government minister, senior military officers and 28 members of the victims' families were traveling to Nias for a memorial service Sunday.

Downer said there was no evidence that a terrorist attack would target the service.

"We have no information that it could take place on Nias Island or be in any way associated with the commemorative ceremony," Downer told reporters in his hometown of Adelaide in southern Australia.