Colonels from the U.N. Command, who met at the border with counterparts from Pyongyang's Korean People's Army, reminded North Korea of the U.N. Security Council order to honor the truce. Officers also proposed a joint task force to discuss the "armistice violations," the military commission said in a statement.
The 100-minute talks, which took place at the "truce village" of Panmunjom inside the Demilitarized Zone dividing the two Koreas, were the second round of talks since the Cheonan went down off the Koreas' west coast on March 26, killing 46 South Korean sailors.
The two sides tentatively agreed to meet again next Thursday, the U.N. Command said.
North Korea vehemently denies involvement in the sinking of the 1,200-ton Cheonan, and has demanded to be allowed to send its own investigators to South Korea to examine the results.
The North proposed that its delegation composed of up to 30 investigators stay in the South for three to five days or even longer to conduct field investigations and that the U.S. guarantee all logistical support, the North's official Korean Central News Agency later reported.
A team of international investigators concluded in May that a North Korean submarine fired the torpedo that sank the warship in what Seoul called the worst military attack on South Korea since the 1950-53 Korean War.
The U.N. Security Council approved a presidential statement earlier this month condemning the incident, but did not directly blame Pyongyang.
The U.N. Command, however, blames North Korea for the incident and considers it a violation of the cease-fire, a command official said Friday, speaking on condition of anonymity because the results of the command's own investigation have not been released.
The meeting took place as a North Korean official threatened a "physical response" if the U.S. and South Korea carry out joint military exercises that U.S. Defense Secretary Robert Gates said would be held to send a "clear message" to North Korea to stop its "aggressive behavior."
North Korean spokesman Ri Tong Il told reporters at an Association of Southeast Asian Nations meeting in Hanoi, Vietnam, that the military exercises would be "another expression of hostile policy against" North Korea. "There will be physical response against the threat imposed by the United States militarily," he warned.
The military drills are to run Sunday through Wednesday with about 8,000 U.S. and South Korean troops, about 20 ships and submarines and 200 aircraft, including the USS George Washington aircraft carrier and the U.S. Air Force's F-22 stealth fighter.
Pyongyang routinely accuses the U.S. and South Korea of staging the military drills as a rehearsal for an attack on North Korea. Washington and Seoul say the exercises are purely defensive and that they have no intention of invading the North.
The North's officers also called on the U.S. to call off the planned military exercises, KCNA said.
The U.S. stations 28,500 soldiers in South Korea to protect the ally against aggression.
Even as tensions were rising, South Korea's President Lee Myung-bak said Friday that Seoul was willing to expand humanitarian assistance for the impoverished rival, the Yonhap News Agency reported.
"President Lee said such a humanitarian aid should continue and stressed more active assistance is necessary to help North Korea," Lee's spokeswoman Kim Hee-jung quoted him as saying.
The about-face by the conservative president comes as Pyongyang faces fewer sources of much-needed aid, with the U.N. Security Council tightening sanctions because of its nuclear defiance and the U.S. announcing new sanctions earlier this week.