U.S. Ambassador to South Korea Mark Lippert was in good condition overall on Friday and is expected to have his stitches removed early next week from injuries inflicted by a South Korean assailant.

Wielding a 25-centimeter knife, Kim Ki-jong slashed the ambassador five times, including a deep gash on his face that extends from his right chin to cheek. Thursday's attack happened at a performance hall in downtown Seoul where the envoy was to give a speech. The wounds required more than 80 stitches.

Kim, 55, said he carried out the attack because he was unhappy about the ongoing military drills between South Korea and the U.S., which he said hampered progress in inter-Korean relations. The Key Resolve and Foal Eagle exercises kicked off earlier this week and are intended to thwart North Korean aggression.

Doctors at Yonsei University's Severance Hospital, where Lippert underwent surgery right after the attack, had said there was no irreversible damage to key facial organs like the nerves and salivary glands. There was, however, a minor injury to the nerves in his left pinkie, which they said should recover in about six months to a year.

Yoon Do-heum, head of the hospital, said the stitches on his face will be taken out either on Monday or Tuesday and doctors will watch the envoy for another day or two before deciding when he may leave the hospital.

Yoon said Lippert barely felt pain in his face, which was the most seriously injured, but told him his left arm and fingers continued to hurt.

"But this kind of pain should go away in about two to three days," Yoon told reporters in a briefing.

The envoy has had no problems moving around within his room, although he wasn't able to sleep until 3 a.m., Yoon said.

At one point, Lippert's temperature rose to 37.7 degrees Celsius but has stabilized to normal levels. There were no signs of infections, but the doctors will keep an eye on his temperature to make sure there are no complications, he added.

Yoon also said Lippert thanked the doctors in Korean and wanted to express thanks to the South Koreans who looked out for him.

Lippert told the doctors he had slept well despite having only gotten four hours of sleep. Yoon said the ambassador appeared to be in better mental condition than the doctors, asking them if they were doing fine.

The envoy had previously written on his Twitter account that he was "doing well and in good spirits."

"Will be back ASAP (as soon as possible) to advance US-ROK alliance!" he wrote, using the acronym of South Korea's official name, Republic of Korea.

Lippert became the youngest-ever U.S. ambassador to Seoul last year. His wife gave birth to a son here, to whom they gave a Korean middle name. He was formerly the assistant secretary of defense for Asian and Pacific security affairs from 2011 to 2012. (Yonhap)