Farmer groups are raising concern over speculation that the government may agree to additionally open the domestic agricultural and livestock markets in the ongoing trade negotiation with the United States.

At a joint rally and press conference in front of the Yongsan presidential office on Friday, the groups, including the Federation of Korean Agricultural and Livestock Association, vowed to fight against a possible move to lift tariffs on U.S. agricultural and livestock produce and non-tariff barriers without consent from farmers.

The groups said the country has become the fifth largest importer of American agricultural and livestock produce since most of the related tariffs were abolished under the bilateral free trade agreement effective 2012.

They said agreeing to further open the agricultural and livestock markets in the tariff negotiation would result in American imports' further encroachment of the domestic market, which would destroy the foundation of local agricultural production.

The groups also urged Trade Minister Yeo Han-koo to resign, after he recently implied that the market opening could be used as a bargaining chip.