China, South Korea and Japan started the fourth round of negotiations on a trilateral free trade agreement (FTA) in Seoul on Tuesday.

The fresh round of negotiations, to last till Friday, focuses on modalities of tariff reduction, opening of the service trade, investment and certain range and fields of the agreement, according to the Chinese delegation.

South Korea's Trade Minister Yoon Sang-jick on Monday told reporters that although these talks may not always go smoothly, the negotiations are "moving toward an end."

South Korean farmers previously opposed such a FTA, fearing that a free trade pact would flood the market with cheap farm products.

The three Asian countries talked about the trilateral FTA's modality such as how to make a draft of liberalization for goods at the third round of negotiation held in Tokyo last year.

China, South Korea and Japan have seen increasingly close economic and trade relations.