SEOUL (Reuters) -South Korea's presidential candidates will face off in their first TV debate on Sunday evening ahead of a snap election on June 3 to choose a successor to former President Yoon Suk Yeol, who was impeached over his short-lived martial law declaration in December. South Korea has begun trade talks with the United States and is seeking a waiver from the tariffs. After U.S. President Donald Trump slapped 25% tariffs on South Korea in April, Seoul was one of the first countries to hold face-to-face talks with Washington, following in the footsteps of Japan.