Earlier media reports said Dung had approved a directive allowing the mining, processing and use of bauxite ore in the mountainous coffee-growing region.
The project has met with protests from scientists and local residents, who fear the open-cut mining will destroy vast forest and crop areas and create mountains of toxic sludge.
On Wednesday Dung told domestic reporters in Hanoi the plan was “a major policy of the party and the state”, according to the government’s website.
It also quoted the premier as saying there would soon be a conference on how to exploit the bauxite resources in a sustainable and efficient way.
Last month Vietnam’s famed war hero General Vo Nguyen Giap, 97, sent an open letter to Dung asking for plans for bauxite mining to be put on hold until international experts had studied the ecological impact.