Philippine President Benigno Aquino has suspended army operations against Maoist guerrillas for a month to mark Christmas and a visit by Pope Francis, the head of the military said on Monday.

The unilateral ceasefire will start at midnight on December 18 and end at midnight on January 19, the day the Pope, the head of the more than 1.2 billion Roman Catholic worldwide, is scheduled to leave the Philippines, General Gregorio Catapang said.

"The declaration of the suspension of military offensive against the New People's Army will highlight the government's sincerity to pursue peace," Catapang said in a statement.

It will be the longest Christmas truce in three decades.

The communist rebels have been fighting to overthrow the government for 45 years. The conflict has killed more than 40,000 people and stunted growth in resource-rich rural areas.

The 4,000-member guerrilla force, largely based in mining areas on the southern island of Mindanao, is expected to declare a shorter truce over Christmas and the New Year.

Law enforcement operations and humanitarian work in typhoon-ravaged areas in the central Philippines, particularly on Samar island where the rebels are active, will, however, go on to ensure safety, Catapang said.

Military spokesman Colonel Restituto Padilla said the truce did not cover the Abu Sayyaf Islamist militant group on the remote southern islands of Basilan and Jolo. The militants are known for kidnapping, bombing and beheading hostages.

Pope Francis is due to arrive in the mostly Catholic Philippines on January 15.