South Korea has threatened to deliver a "firm response" to "provocation" if the North goes ahead with its planned rocket launch.
North Korea's long-range rocket, scheduled to put what it says is a satellite into orbit next week, has been installed on its launch platform, according to the country’s space officials.
Speaking on Monday, Kim Min-seok, South Korea's defence ministry spokesman, said: "We want to clarify that the launch is a provocation that threatens the peace and stability of the Korean peninsula and Northeast Asia.
“The South Korean military is fully prepared to protect the South Korean people and respond firmly against any acts of provocation that threaten the peace and stability of the Korean peninsula."
North Korea maintains that the launch is meant to demonstrate its scientific achievement.
Engineers, insisting the project was for scientific purposes, said the satellite will orbit the earth and send back data for weather forecasts and crop surveys.
Nevertheless, the US, Japan, Britain and other nations have urged North Korea to cancel the launch.
They say that firing the long-range rocket would violate UN resolutions and the country's promise to refrain from engaging in nuclear and missile activity.
The communist nation organised an unprecedented visit to Tongchang-ri space centre to show that the Unha-3 rocket is not a disguised ballistic missile, as claimed by the US and its allies, notably South Korea and Japan.
"To say this is a missile test is really nonsense," Jang Myong-jin, head of the space centre, said.
"This launch was planned long ago, on the occasion of the 100th birthday of [late] president Kim Il-sung. We are not doing it for provocative purposes."
For the first time, North Korea allowed some 50 foreign journalists to go to the new space centre built on the Cholsan peninsula, 50km from the Chinese border.
The journalists were able to observe the rocket, painted in white with sky blue lettering, installed on a platform ahead of its scheduled launch sometime between April 12-16.
Jim Walsh, an international security expert at Massachusetts Institute of Technology, says the launch is aimed at cementing the position of the country’s new leader, Kim Jong-un.
“I think this test is aimed not an international audience- South Korea, US or others. It is aimed internally," he told Al Jazeera from Boston.
Jim Walsh of MIT says the planned rocket launch, at a time of political transition, has internal goals
"I think we have to remember that North Korea is going through a political transition-only the second political transition in its entire history. There is a young leader, this is a about ... I think that message is directed internally."
Kim took over as the country's "supreme leader" after his father, Kim Jong-il, died last december.
“Frankly, this missile test technically, in terms of military capability, means nothing," Walsh said.
"Roughly, this is their fourth test in 15 years. That doesn’t take you far in the missile business."
Last month, Naoki Tanaka, Japan’s defence minister, said Japan could shoot down a North Korean rocket if it entered Japanese airspace.
It even deployed a land-based system of interceptor missiles in preparation for the planned rocket launch.
China, North Korea's main foreign ally, has also expressed its concerns.
The US suspended on March 29 food aid to the North, saying Pyongyang had broken its promise to refrain from missile launches and cannot be trusted to deliver the aid to those who need it.