After a four-year wait, South Korea has authorized E.I. du Pont de Nemours & Co.'s application to build a $97 million titanium dioxide plant jointly with a local firm, the Finance Ministry said Friday. Officials said the proposed plant will be capable of producing anually 60,000 tons of titanium dioxide, a white crystaline compound used as a paint pigment. The American company will put up $77.6 million and control 80 percent of the venture, with the remaining 20 percent invested by Hanyang Chemical Corp., officials said. Strong opposition by local environmentalists who feared pollution had delayed the approval. Sources said the U.S. government recently intervened to get the project approved. The Ministry officials said the approval was conditioned on du Pont burying waste from production. Du Pont is expected to market the product at home and abroad. There is now one small domestic producer. Officials said the final approval came Thursday when the Foreign Capital Project Review Committee met. Hanyang and Du Pont have yet to pick a site for the plant, according to Hanyang officials who did not say when the plant will begin operation. One press report said it will take about three years to build the plant.