Seoul: Industry Minister Kim Jung-kwan returned home Sunday after a trip to the United States, where he held follow-up talks with U.S. Commerce Secretary Howard Lutnick on the bilateral trade agreement reached in July.

According to Yonhap News Agency, Kim had been in the U.S. since Thursday to iron out differences over the details of the trade agreement under which South Korea pledged to invest US$350 billion in the U.S. in exchange for Washington lowering its "reciprocal" tariffs on South Korea from 25 percent to 15 percent.

Kim and Lutnick met at an undisclosed location in New York, but it remains unclear whether they made any significant progress. Upon arriving at Incheon International Airport, the country's main gateway west of Seoul, early Sunday morning, Kim declined to answer reporters' questions about the outcome of the negotiations.

The trade agreement was initially concluded in July and reaffirmed in broad terms during last month's summit in Washington between President Lee Jae Myung and U.S. President Donald Trump. Details of the investment plan remain undecided, however, with South Korea's presidential chief of staff for policy, Kim Yong-bum, recently saying the two sides are at an "impasse."