Washington (CNN) -- Adm. Mike Mullen, the chairman of the U.S. Joint Chiefs of Staff, is headed to South Korea in a hastily planned visit meant to reassure the South Korean military of U.S. support, American officials said.
"The purpose of this trip is to reaffirm our alliance to South Korea," said Mullen's spokesman, Capt. John Kirby. "So the principal message is to the South Koreans that we continue to stand by them in the defense of their territory, for stability on the peninsula."
A second Pentagon official -- who declined to be named -- described the trip as "relatively sudden," adding that Mullen's visit intends to affirm "our commitment to the defense of their territory."
The trip comes as the South Korean navy began live-fire exercises on the seas surrounding the Korean peninsula Monday in the midst of bristling tensions with the North, South Korean media reported.
U.S. officials said the visit was planned last week, brushing off suggestions that Mullen is traveling on an emergency visit.
"Obviously, conditions and the situation remain tense on the peninsula, but I don't believe anyone thinks we are in an emergency situation right now," Kirby said. "That said, it is still tense."
CNN's Charley Keyes contributed to this report