The statement from the North's Committee for the Peaceful Reunification of Korea accused South Korea of "trumpeting about 'sanctions'" ahead of the launch, adding that outsiders would know "what will soar in the air in the days ahead".
"If the puppet warmongers infringe upon our inviolable dignity even a bit... we will not only punish the provokers but reduce their stronghold to debris," it said.
On Friday a South Korean newspaper quoted a government official had stepped up preparations in earnest for the anticipated launch.
The Chosun-Ilbo quoted the unnamed official as saying radar-tracking facilities and other equipment needed for tracking and controlling missiles had been installed at the launch site.
Increased vehicle and human activity was also observed, the paper said.
North Korea has defended what it says is its sovereign right to develop its own space programme.
State media has said the programme is proof of the success of the national philosophy of "juche", or self reliance.
South Korea and the US have both warned the North that it will face severe consequences if it goes ahead with the launch, which they see as a pretext for testing the long-range Taepodong-2 missile.
The Taepodong-2 could theoretically reach Alaska or even the US west coast, but it has never flown successfully.
The North fired a Taepodong-1 missile from Musudan-ri in 1998, in a launch it said placed the country's first satellite into orbit.
The rocket overflew Japan and sparked international condemnation.
In 2006 it fired a longer-range Taepodong-2 from the same site, but the missile failed after about 40 seconds and blew up.
That flight resulted in international sanctions, but was later followed by North Korea's first test of a nuclear weapon.
Analysts have said the latest moves by North Korea are an attempt to draw the attention of the new US administration and ensure it remains a diplomatic priority.