Japan's agency in charge of the extension of the Hokkaido Shinkansen line to Sapporo says it will be extremely difficult to open the line at the end of fiscal 2030.

The project aims to connect Tokyo to Hokkaido's capital city of Sapporo in four and a half hours. The construction covers 212 kilometers from Shin-Hakodate-Hokuto to Sapporo and tunnels account for 80 percent of the distance.

Fujita Kozo, the head of the Japan Railway Construction, Transport and Technology Agency, met transport minister Saito Tetsuo on Wednesday. The meeting was held behind closed doors except at the outset.

Fujita said he reported to the minister that it will be extremely hard to meet the opening target date due to delays in construction.

He said huge rocks were found during tunnel construction, forcing the work to be suspended. He also said it is difficult to secure workers due to the tightening of regulations on overtime work in the construction industry.

The transport minister reportedly said he plans to hold a meeting of a government expert panel to examine the agency's report and will decide whether to postpone the opening of the line.

Fujita also said there are technological problems in the construction and that even if the opening is postponed, it is difficult to specify a new timeframe.

Fujita said the agency estimates the project will be delayed several years. Its possible delay is expected to affect development plans of the communities along the planned extended line.