Commonwealth Attorney General Philip Ruddock, however, said he expected the nation's overall security threat level designation to remain at medium as Bush and leaders of some 20 countries attend the Sydney summit of the Asia-Pacific Economic Cooperation organization.

"It would be naive to suggest that simply because you were having a conference the threat level would change," he told The Australian. "I suspect it wouldn't."

The warning about possible use of the SAS in Sydney came from a professor at the University of Western Sydney, who said last year's Commonwealth Defense Act gave new powers on troop mobilization to the federal government.

"Any perceived security threat to the APEC participants, whether an alleged terrorist plot or political protest, could see the heavily armed SAS Tactical Assault Group called out on Sydney streets," Associate Professor Michael Head reportedly told the newspaper.

Australia, following Britain's example after the 2005 London bombings, has tightened domestic anti-terrorist security and pays close attention to possible Islamists within its Muslim communities.

The premier of the state of New South Wales, Morris Lemma, said Thursday new legislation may be introduced to give police special powers to randomly detain and search people in Sydney during the summit for security reasons.

Lemma met with Ruddock in Sydney Wednesday to discuss security arrangements for the summit. Other national leaders attending in addition to Bush are Russian President Vladimir Putin and Chinese President Hu Jintao.