South Korean President Moon Jae-in speaks at the Seoul press center in Seoul, South Korea on Sept. 20, 2018.  (Xinhua/Wang Jingqiang)

US authorities for the first time filed a complaint against South Korea under environmental rules of the free trade pact between Seoul and Washington, over illegal fishing, the government announced Thursday.

The US Trade Representative's office said it "intends to seek environment consultations" with Seoul under the terms of the US-Korea Free Trade Agreement, the first step in a formal trade complaint.

The trade representative's office cited a government report that named South Korea, saying the country failed to stop its vessels from "engaging in fishing activities that violate conservation and management measures."

In a report also released Thursday, the US National Marine Fisheries Service said in late 2017 two South Korean-flagged vessels used long-line gear within 24 hours of the notified closure of a fishery in violation of international rules.