BRUSSELS (Reuters) - Ministers from European Union countries on Tuesday approved a landmark free trade agreement with Vietnam, which will reduce tariffs on 99% of goods over a period of 10 years.The bloc hopes the accord, the first of its kind with a developing country in Asia and second with a member of regional association ASEAN, will be a stepping stone towards a wider EU-Southeast Asia trade deal. It also covers investments.An EU-Singapore deal is set to enter force later this year.The two..