"Gen. Thurman visited Seoul as chief of Army Forces Command and his visit was scheduled long before his nomination," the official said on the condition of anonymity.
Thurman, currently commander of the U.S. army's largest organization, was scheduled to meet South Korean Defense Minister Kim Kwan-jin before returning home late Tuesday, the official said.
On Monday, Thurman observed the ongoing Key Resolve/Foal Eagle exercises, annual drills by South Korean and U.S. forces set to end on Thursday and met Gen. Han Min-koo, chairman of the South's Joint Chiefs of Staff, military officials here said.
The peninsula-wide joint drills come as tensions have been running high since North Korea's two deadly military attacks last year that killed 50 South Koreans.
A South Korean warship sank last March from a North Korean torpedo attack, killing 46 sailors. In November, the North shelled a South Korean border island in the Yellow Sea, killing four people, including two civilians.
Thurman will take the helm of the USFK in June and oversee defense of South Korea at a turbulent time in which both Seoul and Washington remain vigilant against possible North Korean attacks on the South this year.
Last week, North Korea tried to disrupt GPS (global positioning system) signals in the South's capital by using jamming equipment, military officials here said.
The jamming signals were believed to be sent from the North's military and might have been designed to disrupt the South Korean-U.S. joint military drills, according to officials.
Also last week, some 40 Web sites in Seoul came under attack by a malicious computer virus, including the official site of the presidential office Cheong Wa Dae. No serious damage has been reported and it was not immediately known who was behind the attack.
However, the South's military raised its alert status on cyber warfare readiness, called "Infocon," by a notch to the fourth-highest level, in response to the latest cyberattack, military officials said.
About 28,500 U.S. troops are stationed in South Korea, a legacy of the 1950-53 Korean War.