Sin, the de facto leader of the Roman Catholic church here, provided no details of the alleged plotters or his sources, but his revelation came two days after Arroyo said there was "understandable restiveness" in the military ranks.

"Be ready to move to whatever action may be called for and necessary to guard our president and the legitimate government and to keep our nation in the way of peace," Sin said in a statement.

While acknowledging that government reform was needed, Sin said it should be done "through peaceful means and deeds of justice and peace on the part of our leaders and of every one of us."

"We believe it is our duty to make ourselves intelligently alert and vigilant in the present situation so that the common good of our people may prevail," Sin said.

The Philippines is the bastion of Catholicism in Asia, with more than 80 percent of the country's 80 million people practicing Roman Catholics.

In 2001, Sin mobilized his flock to support a peaceful uprising that forced the ouster of former president Joseph Estrada, now in jail on charges of corruption.

Sin was also a key figure in a similar uprising that toppled strongman Ferdinand Marcos in 1986, and remains among the most politically influential personalities in the Philippines.

Hundreds of soldiers were moved into Manila Friday to tighten security ahead of Arroyo's annual state of the nation report to Congress on Monday.

An Army battalion would secure the armed forces headquarters "to beef up security reserves" for the address while a special forces company was to move to Army headquarters in Manila before being redeployed to the south, the government said.

Military and defense officials have denied any attempts to destabilize the government, even as Arroyo acknowledged she met with junior military officers last week to address their complaints.

"There has been some understandable restiveness, but I have resolved this matter directly with the troops," Arroyo said as she sought to ease worries of a coup that have sent financial markets tumbling.

The Philippines suffered seven bloody coup attempts in the late 1980s, setting back economic development for years.

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