Containers pile up at?Qingdao Port, Shandong Province. [File photo]

Delegates from China, Japan and the Republic of Korea (ROK) have concluded negotiations over an investment treaty, and the three countries promised to go through domestic process as soon as possible, China's Ministry of Commerce (MOC) said Thursday.

After three days of talks in Beijing, the three countries reached a "substantial consensus" on issues concerning the treaty and signed a protocol based on the negotiations, the MOC said in a statement posted on its website.

Negotiations over the trilateral investment treaty began in 2007. It was regarded as the foundation for the building of a free trade area between the three countries.

The MOC previously said that it hopes to start negotiations on the free trade area at the fifth trilateral leaders' meeting in May.