MANILA (Reuters) - The Philippines has begun preparations for the burial of late dictator Ferdinand Marcos at a cemetery for national heroes, a decision that drew criticism from the vice president and could polarise the country.

President Rodrigo Duterte said he was fulfilling a campaign promise to have Marcos, who ruled with an iron fist for two decades, interred at the heroes' cemetery as a former president and soldier.

On Sunday, Defence Secretary Delfin Lorenzana assigned armed forces chief of staff General Ricardo Visaya, to handle arrangements for the burial next month, in line with "the verbal order of the president to implement his campaign promise".

"I am just implementing a presidential directive, whatever I think is immaterial," Lorenzana told reporters on Monday.

"He deserved to be buried at the heroes' cemetery based on the criteria from the military regulations."

Marcos was a soldier and guerrilla leader during World War Two when the former U.S. colony was occupied by Japanese forces.

As a dictator in the 1970s and '80s, Marcos, his family and cronies amassed an estimated $10 billion in ill-gotten wealth and thousands of suspected communist rebels and political foes were killed. His wife, Imelda, denies amassing wealth illegally.

Vice President Leni Robredo said she opposed Duterte's decision to transfer the strongman's remains from his home town of Batac in the northern Philippines to the cemetery.

"Mr Marcos is no hero," she said in a statement. "How can we allow a hero's burial for a man who has plundered our country and was responsible for the death and disappearance of many Filipinos?"

Robredo, a human rights advocate, defeated the dictator's son and namesake, Ferdinand Marcos, in a vote for the vice presidency in May.

She said Duterte's decision would not bring unity but would "deepen the unhealed wounds" of Marcos' victims.

Some Roman Catholic bishops and left-wing activists also opposed Marcos' burial.

"It is a great insult," said one prominent bishop, Arturo Bastes.

Duterte brushed off the criticism.

"I see nothing wrong in having Marcos buried at the Libingan ng mga Bayani," the president said in a speech to soldiers on Sunday, referring to the cemetery.

Marcos was elected president in 1965 and re-elected four years later but imposed martial law a year before his second term ended.

In 1986, he was ousted in a "people power" revolt and fled to Hawaii where he died three years later. His remains were returned in the early 1990s and have been kept in a family mausoleum.

(Reporting by Manuel Mogato; Editing by Robert Birsel)