(Reuters) -South Korea has elected liberal Lee Jae-myung as president to lead the country through a tumultuous period that will require negotiating trade tariffs with the U.S. and mending the scars from his ousted predecessor's shock martial law declaration.

The U.S. ally has been without a permanent leader since late last year, when Yoon Suk Yeol was impeached over his botched declaration of martial law.