Russian counterparts building the first stage of the Korea Space Launch Vehicle-1 had called for more time for testing, said spokesman Kim Hong-Gab.

The launch date was previously set for on or around July 30, depending on the weather.

"It's now hard to meet the original schedule. We have to negotiate with the Russians on a new launch date," the spokesman told AFP.

It was the third time that South Korea has postponed the much-touted launch.

Blast-off was delayed from late 2008 to late June this year after China's Sichuan earthquake last year caused problems securing key parts. The launch was again delayed until late July to give engineers more time for tests.

Seoul plans to launch a satellite weighing 100 kilograms (220 pounds) into a low earth orbit from the Naro Space Centre in Goheung, 475 kilometres (300 miles) south of Seoul.

North Korea in April fired a rocket to, it claimed, launch a satellite but the United States and its allies say that launch was really intended to test a long-range missile.

South Korea is eager to join Asia's space race. In November 2007 it announced a plan to launch a lunar orbiter by 2020 and send a probe to the moon five years after that.

It unveiled the project one month after China launched its first lunar orbiter and two months after Japan did.

In April last year Seoul sent its first astronaut into space aboard a Russian Soyuz rocket.

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