Story highlights North Korea says the rocket will carry an Earth observation satellite

The launch is scheduled to take place between Thursday and Monday, North Korea says

South Korea says it will "respond with appropriate countermeasures"

A launch would breach U.N. Security Council resolutions

North Korea said the assembly of a rocket it plans to launch in the coming days should be completed Tuesday, setting the stage for a move that has been widely criticized by other nations.

The launch will take place at some point between Thursday and Monday as previously noted, Ryu Kun Chol, a senior North Korean space official, told reporters in Pyongyang.

North Korea has said that the rocket will carry into orbit an Earth observation satellite to aid North Korea's economic development. Japan, the United States and South Korea see the launch as a cover for a long-range ballistic missile test.

Ryu, the deputy director of the Space Development Department of the Korea Space Technology Committee, said Tuesday that it was unreasonable to say this would be a ballistic missile test in disguise.

The act of firing the long-range rocket would breach U.N. Security Council resolutions, and Washington has suspended a recent deal to provide food aid to North Korea as a result. Japan has said it would shoot down the rocket if it were to enter its territory.

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The South Korean defense minister, Kim Kwan-jin, discussed the planned launch with his U.S. counterpart, Leon Panetta, by phone, an official from the South Korean Defense Ministry said Tuesday.

Kim and Panetta agreed that the launch would be a "grave provocation," the official said.

South Korea would "respond with appropriate countermeasures," the country's Reunification Ministry said in a statement without elaborating.

The last time Pyongyang carried out what it described as a satellite launch, in April 2009, the U.N. Security Council condemned the action and demanded that it not be repeated.

"Let me make absolutely clear," U.S. Secretary of State Hillary Clinton told reporters Tuesday. "Any launch by North Korea would be a serious, clear violation of their obligations under already existing U.N. Security Council resolutions 1718 and 1874."

Adding to the tensions, a recent report from South Korean intelligence officials suggests that North Korea is planning a new nuclear test in the area where it staged previous atomic blasts.

The South Korean intelligence report noted that the two previous rocket launches that Pyongyang said were intended to put satellites into orbit were followed a few weeks or months later by nuclear tests.

China, North Korea's closest ally and largest provider of aid, has expressed concern about the planned launch. Beijing says it has held talks with Pyongyang on the matter.

"China strongly encourages everyone involved to remain calm and reasonable," said the Chinese foreign minister, Yang Jiechi, according to a report Monday by the official Chinese news agency, Xinhua. "These issues need to be worked out in a diplomatic and peaceful manner."

Analysts say the planned trajectory of the multistage rocket would be north to south over the Yellow Sea, with the main body of the projectile landing in the Pacific Ocean near the Philippines.

President Benigno Aquino III of the Philippines has condemned the planned launch as a "needless provocation" that could increase tensions in East Asia.

Several airlines operating in the region have said they will change flight routes during the launch window.

Philippine Airlines is rerouting more than 10 flights; All Nippon Airways is altering five flights, and Japan Airlines is altering four.