SEOUL - North Korea announced yesterday that it would attempt to launch a long-range rocket in mid-December, in violation of a UN ban on its nuclear and missile programs.

The launch, set for mid-December, is likely to heighten already strained tensions with Washington and Seoul. This would be North Korea's second launch attempt under leader Kim Jong Un, who took power following his father Kim Jong Il's death nearly a year ago. The announcement by North Korea's space agency followed speculation overseas about stepped-up activity at North Korea's west coast launch pad captured in satellite imagery.

A spokesman for North Korea's Korean Committee for Space Technology said scientists have "analyzed the mistakes" made in the failed April launch and improved the precision of its Unha rocket and Kwangmyongsong satellite, according to the official North Korean Central News Agency.

The space agency said the rocket would be mounted with a polar-orbiting earth observation satellite, and maintained its right to develop a peaceful space program.

Washington considers North Korea's rocket launches to be tests of technology for long-range missiles designed to strike the United States, and such tests are banned by the United Nations.

North Korea is not known to have succeeded in mounting an atomic bomb on a missile, but is believed to have enough weaponized plutonium for at least half a dozen bombs, according to U.S. experts. In 2010, it revealed a uranium enrichment program that could provide a second source of material for nuclear weapons.

Six-nation negotiations on dismantling North Korea's nuclear program in exchange for aid fell apart in early 2009.

Some analysts question whether North Korean scientists have corrected whatever caused the misfire of its last rocket.

"Preparing for a launch less than a year after a failure calls into question whether the North could have analyzed and fixed whatever went wrong," David Wright, a physicist with the Union of Concerned Scientists, wrote this week.

North Korea under its young leader has pledged to bolster its nuclear arsenal unless Washington scraps what the North calls a "hostile" policy. North Korea maintains that it is building bombs to defend itself.

Before its last two rocket launches, North Korea notified the International Civil Aviation Organization and the International Maritime Organization of its intentions to launch.