* Former minister Lopez imposed the ban
* Miners say it is the only viable extraction option
* Philippines is world's top nickel ore exporter (Adds comment from mining group, background)
MANILA, Sept 5 (Reuters) - Philippine President Rodrigo Duterte said on Tuesday he agreed with banning open-pit mining in the world's top nickel ore exporter given the environmental damage it causes but would give mining firms time to find other ways to extract minerals.
Duterte said in a televised speech that the extraction process was a "dangerous environmental activity" and that he had asked Environment and Natural Resources Secretary Roy Cimatu "to look into the eventual closure of open-pit mining."
"I agree with (former Environment Secretary) Gina Lopez that that has to stop some time. But I'll give the mining companies enough elbow room ... for eventual change in the modality of getting what's inside the bowels of the earth," Duterte said.
Open-pit mining is allowed by the country's mining law but Lopez banned it during her 10 months in office, saying it killed the economic potential of places where it was done.
The ban was one of several measures Lopez imposed during a crackdown on the sector that included closing or suspending 26 of the country's 41 mines.
Lopez was replaced by Cimatu in May after she failed to be confirmed in her post by lawmakers.
Cimatu said in July that he would not lift the open-pit ban but had yet to decide on the fate of shuttered mines.
A ban would halt the $5.9 billion Tampakan copper-gold project in South Cotabato province in Mindanao island, the nation's biggest stalled mining venture.
Tampakan failed to take off after the province where it is located banned open-pit mining in 2010, prompting commodities giant Glencore Plc to quit the project in 2015.
Lopez has said the project would cover an area the size of 700 soccer fields in what otherwise would be agricultural land.
But a miners' group said open-pit mining was the only viable way to extract minerals in the Philippines where most ore is near the surface and low grade.
"Open-pit mining per se is not bad," Ronald Recidoro, spokesman for the Chamber of Mines of the Philippines told reporters on the sidelines of an industry conference.
"Compared to underground mining, open pit mining is safer. Also cost efficient." (Reporting by Manolo Serapio Jr; additional reporting by Enrico dela Cruz; editing by David Clarke)