High-speed train services connecting Seoul and its suburbs with the southeastern region will be expanded to cities elsewhere in the country by 2020, the transportation ministry said.

A bullet train ride from Seoul to the southeastern port of Busan, one of the most distant cities from the capital, currently takes about two-hour-and-a-half hours but that time will be dramatically cut by the upgrade in infrastructure.

"The bullet train service travelling at least 230 kilometres (143 miles) per hour will eventually be accessible to 83 percent of the whole population from the current 60 percent," the ministry said in a statement.

The project, expected to cost 16 trillion won ($14.6 billion), will help cut national greenhouse gas emissions by 7.7 million tonnes a year by encouraging more people to use trains instead of cars, it said.