SEOUL, South Korea - North Korea has moved up the window of its planned long-range rocket launch to February 7-14, South Korea's Defense Ministry said Saturday. The launch, which the North says is an effort to send a satellite into orbit, would be in defiance of repeated warnings by outside governments that suspect it is a banned test of ballistic missile technology.

North Korea did not inform international organizations of any other changes in its plan, and the rocket's expected flight path remains the same, said South Korean Defense Ministry spokesman Moon Sang Gyun, adding that the South believes the launch could come as soon as Sunday.

The North informed the International Maritime Organization and other related agencies on Tuesday that it would attempt a satellite launch between February 8 and 25. No reason was given Saturday for the change of dates.

North Korea's launch declaration came just weeks after it conducted its fourth nuclear test. Outside experts and officials say that each nuclear test and long-range missile launch brings the North closer to creating a nuclear warhead small enough to fit on an intercontinental missile capable of reaching targets as far as the U.S. West Coast.

South Korea believes that the North has completed all launch preparations, including strapping the rocket onto a launch tower and injecting fuel, and that there is a high possibility the launch will take place on Sunday, Moon said.

He said that a possible explanation for the date change was that Sunday's weather conditions were forecast to be favorable for a launch.

Recent commercial satellite imagery analyzed by U.S. researchers showed tanker trucks at the launch pad at North Korea's Sohae facility, which likely indicates the filling of fuel and oxidizer tanks in preparation for the launch.

The Associated Press contributed to this report.