US President Donald Trump and South Korean President Moon Jae-in address the media prior to dinner in the State Dinning Room at the White House on June 29, 2017 in Washington, D.C.

The United States notified South Korea on Wednesday it plans to start negotiating amendments to a five-year-old free trade agreement with Seoul and called a meeting to kick off the talks for next month.

The announcement came months after U.S. President Donald Trump said he would either renegotiate or terminate what he called a "horrible" trade deal.

U.S. Trade Representative Robert Lighthizer, acting on Trump's instructions, said the joint committee under the U.S.-Korea Trade Agreement (KORUS) would meet in Washington next month. No date has been set.

"Since KORUS went into effect, our trade deficit in goods with Korea has doubled from $13.2 billion to $27.6 billion, while U.S. goods exports have actually gone down," Lighthizer said in a statement.

"This is quite different from what the previous Administration sold to the American people when it urged approval of this Agreement. We can and must do better," he said.

Trump, in an interview with Reuters in April, blamed the trade deal on his 2016 Democratic presidential election opponent, Hillary Clinton, who as secretary of state promoted the final version of the agreement before its approval by Congress in 2011.

"It's a horrible deal, and we are going to renegotiate that deal or terminate it," Trump said in the interview.