A strike by South Korean truckers is estimated to have cost 1.6 trillion won ($1.23 billion) in lost shipments, the industry ministry said on Thursday, as a lengthy strike becomes more likely with the government and union far from a compromise.

Disruptions to the country's supply chain expanded on Thursday, the eighth day of the nationwide strike by more than 20,000 truckers, as the government prepares to order more of them back to work.

The cement, steel, auto and oil refining industries have seen 1.6 trillion won in lost shipments in seven days since the strike began last week, the ministry said in a statement.

This includes 562,600 tonnes of steel worth 731.3 billion, 6,707 cars worth 319.2 billion won, and 259,238 kilolitres of oil products valued at 442.6 billion won stuck in transit, it said.

No date has been set yet for the next round of negotiations. Two people at the meeting on Wednesday said shouting erupted during Wednesday's meeting between the government and strike organiser Cargo Truckers Solidarity Union (CTSU).

The government has said it would not expand a minimum pay system for truckers beyond a further three years, which the union says should be permanent and wider in scope.

Kumho Tire Co Inc, South Korea's No. 2 tire maker, which makes 65% of its sales from exports, told Reuters it is cutting 15% to 40% of production output at its two factories until Dec. 6 because the strike has disrupted shipments.

Member companies of Korea International Trade Association (KITA) said in a statement that fresh produce such as fish and kimchi had been scrapped because industrial hubs are blocked, without citing exact figures.

Exports at Samsung Electronics' Gwangju plant, which mainly produces refrigerators and air conditioners, have been halted, although raw materials and other shipments were moving normally, Yonhap news agency reported, citing a plant official.

Samsung Electronics said it is monitoring the situation.

The government is preparing to potentially order oil industry truckers back to their jobs, the industry ministry said on Thursday, after it issued an unprecedented order to force 2,500 cement industry truckers back to work this week. As of Wednesday, 350 of those drivers had been served those orders.

Refusing to get back on the road after a "start work" order can be punished by a fine or jail time, and cost drivers their licenses. ($1=1,300.7900 won) (Reporting by Heekyong Yang, Choonsik Yoo and Joyce Lee; Editing by Clarence Fernandez and Himani Sarkar)