"North Korea's development of long-range missiles is an act of grave provocation that threatens the peace and stability not only of South Korea, but also the region and the entire international community."
"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 foreign minister
He added that the North's nuclear and missile programmes together were a "serious threat" to international security, describing the missile as "not a mere conventional weapon."
"The combination of its long-range missile and nuclear capability will have a very serious impact on the world's peace and security."
On Monday the North signalled it would go ahead with the test despite warnings from the United States, South Korea and Japan.
That statement coincided with the arrival in Asia of Hillary Clinton, the new US secretary of state, who is in the region on her first overseas tour since taking the post.
During her first stop in Japan, Clinton warned North Korea against going ahead with any missile test, saying on Tuesday that such a launch would be "very unhelpful" and that Washington was watching Pyongyang's moves very closely.
According to reports citing South Korean and US intelligence, North Korea is believed to be preparing to test its longest-range missile, the Taepodong-2.
Multi-stage, solid fuel missile thought to have range up to 4,300km.
With modifications extending range up to 7,000km it would be capable of hitting the US west coast.
First tested in July 2006 and flew for about 40 seconds before it destructed, US officials say.
Intelligence agencies believe North Korea has not yet mastered building a nuclear warhead small enough to fit on a missile.
The missile has never flown successfully but is thought to have been designed to reach as far as Alaska or the west coast of the US.
The North contends that the missile is part of a "space development" programme, a term it has used in the past to describe a missile test.
The UN Security Council imposed sanctions on the North after it launched the Taepodong-2 in 2006.
That test was widely considered a failure, with the rocket blowing up less than a minute into flight.
Unfazed by the UN's actions, North Korea conducted its first nuclear test three months later – a move that saw the imposition of even more sanctions.