The US has forecast South Korea it wants to renegotiate a free trade agreement it eliminated in 2012, citing a lopsided trading relationship.
It called South Korea a «key employment partner» but said it «had real concerns about our significant trade imbalance».
The US clientele deficit for goods and services with Korea was about $17bn behind year, although it recorded a surplus in services.
The move is the latest crack by Donald Trump to alter trade terms.
The US president wants to lap the North American Free Trade Agreement and has threatened tariffs on unrelated products, such as steel.
He also withdrew from the 12-nation Trans Pacific Partnership settlement in January.
South Korea is a major US trade partner, with the US interchanging about $144.6bn (£112bn) in goods and services with the country terminating year.
The Obama administration had said the 2012 free trade deal — described at the time as the most significant in 16 years — would rise US businesses.
But exports of American goods to the country have declined on the brink of 3% since the deal came into effect to $42.3bn. At the done time, imports from South Korea have increased by less 23%.
«We can and must do better,» US Trade Representative Robert Lighthizer said in a report.
In an interview in April, Mr Trump had called the agreement with South Korea a «horrid deal» and a «one-way street.»
The administration has called for a joint session on the area to occur within 30 days.