Public companies will play a greater role in building South Korea's social overhead capital as state tax earnings are diverted to other sectors, the government said Wednesday.

The government's fiscal management plan for the 2015-2019 period showed state spending in SOC decreasing over the next four years, with public companies such as Korea Airport Corp. and Korea Expressway Corp. expected to pick up the slack.

The budget for infrastructure building will fall from 24.8 trillion won ($20.7 billion) this year to 23.3 trillion won in 2016, 21.1 trillion won in the following year and to 19.7 trillion won in 2018 before settling at 18.7 trillion won in 2019.

The steady drop represents a 6.8 percent annual decrease over the cited period.

The government said that it will spend the saved money on welfare and upgrading the country's social security net as well as creating more job opportunities.

Of the eight main SOC fields, only air transportation and logistics will receive more money up till 2019, while those related to such areas as road building, railways, ports, urban development and industrial parks will all receive less.

The plan showed taxpayers money earmarked for air transportation and logistics rising at an annual average of 5.8 percent and 0.4 percent each until 2019. In contrast, the budget for industrial complexes will plunge an average 18.6 percent annually, with numbers for roads and urban development dropping 8.6 percent, respectively.

To make up for the drop in spending that could adversely affect the country's infrastructure and economic growth as a whole, the government said it will encourage public companies to play a part in large building projects.

"Even now, public companies with the support of state funding are building roads and railways," a ministry official said. "An efficient and practical way to get state-controlled companies more involved in SOC will be devised."

Under this arrangement, KAC will be tasked with building passenger terminals and parking lots for the airports to be built on Ulleung and Heuksan islands, while the government will construct the runways and airplane aprons.

Seoul announced it will build small airports that can accommodate 50-seat planes on the two islands by 2020 and 2019, respectively.

In regards to road construction, the finance ministry said the role of Korea Expressway Corp. will be expanded so more roads can be built, which can reduce logistics costs and ease travel burdens. (Yonhap)