In addition to four failed launches, North Korea has unveiled missiles designed to target U.S. soil and has tested two atomic devices in recent years. It has not yet proven to have mastered the technology for mounting a nuclear warhead to a long-range missile, however.
A successful launch would mean North Korea could develop an intercontinental ballistic missile capable of striking the U.S. mainland within two to three years, said Chong Chol-Ho, a weapons of mass destruction expert at the private Sejong Institute near Seoul.
Six-nation negotiations to offer North Korea much-needed aid in exchange for nuclear disarmament have been stalled since early 2009.
Last week, U.S. Secretary of State Hillary Rodham Clinton said Washington was deeply concerned, and urged foreign ministers from NATO and Russia to demand that Pyongyang cancel its plans. Moscow joined calls on Pyongyang to reconsider.
China, North Korea's main ally and aid provider, also noted its concern, acknowledging North Korea's right to develop its space program but urging Pyongyang to harmonize the bid with restrictions — including those set by the U.N. Security Council.
International pressure and the prospect of dialogue may be a factor in the delay, analysts in Seoul said.
China must have sent a "very strong" message calling for the North to cancel the launch plans, said analyst Baek Seung-joo of the South Korean state-run Korea Institute for Defense Analyses.
North Korea may also be holding off if the U.S., its longtime Korean War foe, actively engages Pyongyang in dialogue, said Koh Yu-hwan, a professor of North Korean studies at Seoul's Dongguk University.
Associated Press writer Mari Yamaguchi contributed to this report from Tokyo.
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