SEOUL (AFP) - South Korea and the United States called on North Korea Friday to drop its "inhumane" and "belligerent" threats against commercial flights passing through the communist state's airspace. The North late Thursday announced it could not guarantee security for South Korean flights near its territory, saying an imminent major US-South Korean military exercise could trigger a war. Seoul urged Pyongyang to immediately retract the threat, which has forced commercial airlines to divert flights, while the US State Department described the latest comments from Pyongyang as "counterproductive." The US-led United Nations Command (UNC) also called on the North to backtrack and said its move raised "great concern" in international circles. Officials said some 200 flights by Korean Air and Asiana would be re-routed over the next two weeks, adding up to an one hour to journey times. Airlines from other nations using the route over North Korean-controlled airspace are unaffected. The communist state's announcement was the latest in a series of threats that have raised tensions in recent weeks. "The government urges North Korea immediately to withdraw military threats against civilian air flights," Seoul's unification ministry said in a statement. "A military threat to the normal operations of civilian airplanes not only violates international rules but is also an inhumane act that can never be justified." In Washington, the State Department's acting deputy spokesman Gordon Duguid told reporters that "North Korea's belligerent rhetoric is unwarranted and counterproductive to the goal of more constructive engagement." "It's particularly unacceptable that they pose a threat to international civil aviation and global commerce," Duguid added. The North said it could not ensure the safety of South Korean flights passing near its territory over the Sea of Japan, because the 12-day exercise starting south of the border Monday could spark off a conflict. Pyongyang every year denounces the Key Resolve-Foal Eagle exercise as a rehearsal for invasion, while the UNC says the drill is purely defensive. But inter-Korean tensions are running high this year after the North on January 30 announced it was scrapping all peace accords with the South. North Korea is also preparing to fire a rocket from a base overlooking the Sea of Japan for what it calls a satellite launch. Seoul and Washington say the real purpose is to test a missile that could theoretically reach Alaska. South Korean ships will also be re-routed well clear of North Korean waters amid rising tensions, a security official told AFP on condition of anonymity. On Friday generals from the North and the UNC met at the border village of Panmunjom to discuss ways to ease tensions. The UNC said in a statement it told the North Koreans the airspace announcement "was entirely inappropriate, had raised great concern in the international aviation community, and should be retracted immediately." Meanwhile, the North defended the satellite launch as an "independent" right, according to its official Korean Central News Agency (KCNA). It quoted a North Korean general as saying Thursday's move was "an entirely just measure for self-defence." Pyongyang is angry at South Korea's conservative leader Lee Myung-Bak, who scrapped his predecessors' policy of virtually unconditional aid to the North. Speaking during a state visit to Indonesia, Lee said he hoped North Korea would give a "positive response" to his country's concern over Pyongyang's proposed missile launch. Analysts say North Korea may trying to test the resolve of the Obama administration and to strengthen its hand in future nuclear disarmament negotiations. Meanwhile, South Korea's President Lee Myung-Bak said Friday he hoped North Korea would give a "positive response" to his country's concern over its fears the Stalinist state is preparing a missile launch. He said he hoped Pyongyang would respond through the nations involved in six-party talks on the North's denuclearisation - South Korea, the United States, China, Russia and Japan. "South Korea has been trying to communicate with North Korea and hopes that North Korea will give a positive response through the six-party talks," he said during a state visit to Indonesia. Speaking after meeting Indonesian President Susilo Bambang Yudhoyono on the final leg of a three-nation trip including New Zealand and Australia, he said the situation on the Korean peninsular required "international attention." His trip coincided with a spike in tensions over Pyongyang's plans to launch what it calls a satellite and what Seoul and Washington believe is a long-range missile test. North Korea late Thursday announced it could not guarantee security for civilian flights near its territory, ahead of a major US-South Korean military exercise which Pyongyang said could trigger a war. Pyongyang is unhappy with Lee's decision to scrap his predecessors' policy of virtually unconditional aid to the North. Analysts say North Korea may be testing the resolve of the Obama administration in Washington and trying to strengthen its hand in future negotiations on nuclear disarmament.