Each untreated patient could infect five to 10 people a year, and an uncontrolled local epidemic could spread across national borders, it said.
"Only one percent of the estimated 150,000 people with multidrug-resistant tuberculosis (MDR-TB)... in East Asia and the Pacific are getting appropriate treatment," the WHO said in a statement.
"We are more vulnerable than ever to the MDR-TB threat," it said. "Countries must act responsively to safeguard global health."
"MDR-TB raises the risk of a TB epidemic that would be costly and complex to control" as drugs to treat it "are about 100 times more costly than the regimen for normal TB," the UN agency said.
Despite the discovery of a cure half a century ago, TB remains the leading infectious disease killer of adults after HIV/AIDS, according to the WHO.
MDR-TB is caused by mismanagement of standard TB treatment. Mismanagement of MDR-TB can result in extensively drug-resistant TB (XDR-TB), a form of TB resistant to all the most effective drugs and virtually uncurable, it said.
"MDR-TB is a serious problem in China and the Philippines, and of concern in Mongolia, the Republic of Korea and Vietnam," it said. "MDR-TB -- but not standard TB -- is severely neglected" in the region, it said.
"Politicians should commit to action. They need to wake up and realize what is at risk. This is a disease that you can transmit in a cough to your children," it said.