Seoul - North Korea faces international sanctions if it carries through with an upcoming missile launch, South Korean Foreign Minister Yu Myung Hwan warned Wednesday.

North Korea's missile programme represents a serious threat to world security because Pyongyang could link it with its nuclear programme, the minister added.

"North Korea's missile is not a mere conventional weapon," Yu was quoted as saying by the national news agency Yonhap at a meeting in Seoul with foreign diplomats. "The combination of its long-range missile and nuclear capability will have a very serious impact on the world's peace and security."

South Korean officials have said that North Korea has been planning a launch of its Taepodong-2 intercontinental ballistic missile for weeks.

Meanwhile, a South Korean newspaper reported that the North is operating an underground facility to enrich uranium.

The Dong-a Ilbo newspaper cited an unnamed senior government source as saying that small amounts of highly enriched uranium, which can be used to make nuclear weapons, could be produced at an underground site near North Korea's main nuclear facility in Yongbyon, 100 kilometres north of Pyongyang.

The United States said that in the course of negotiations aimed at ending North Korea's nuclear weapons ambitions, Pyongyang admitted that it was pursuing uranium enrichment, but North Korea later denied it.

On Monday, North Korea admitted for the first time that it was readying the launch of a multiple-stage rocket but said it was for "space development," not a missile test.

Whether the North launches a satellite or missile, such an incident would represent a violation of UN resolutions, Yu said.

A missile test or satellite launch is not very different from a technical point of view, he argued, and either would "certainly" lead to sanctions.

A resolution adopted by the United Nations in 2006 after a series of North Korean missile tests demanded the country halt its ballistic missile programme, and included economic sanctions.

South Korea has speculated that North Korea is preparing to test a Taepodong-2 missile under the guise of a satellite launch, as it did in 1998 when it fired a Taepodong-1 over Japanese territory.

According to the US military, the Taepodong-2, when technically perfected, could reach the US state of Alaska and carry a nuclear warhead.

Amid the tensions on the Korean Peninsula, the United States and South Korea announced that their militaries would hold annual joint exercises March 9-20.

North Korea was informed of the manoeuvres, they said, calling the exercises "defence-oriented."

North Korea regularly criticizes such exercises as preparations for an attack on the North. (dpa)