Updated at 8:11 a.m. ET: PYONGYANG -- North Korea said on Wednesday it was injecting fuel into a long-range rocket "as we speak'' ahead of a launch condemned by its neighbors and the West.
The launch is set to take place between Thursday and next Monday and has prompted neighbors such as the Philippines to re-route their air traffic just in case.
Japan said it would shoot down the rocket if it crossed its airspace.
The launch of the Unha-3 rocket, which North Korea says will merely put a weather satellite into space, breaches U.N. sanctions imposed to prevent Pyongyang from developing a missile that could carry a nuclear warhead.
"I think the fuel injection will be completed at an appropriate date,'' Paek Chang-ho, head of the satellite control center of the Korean Committee of Space Technology, told a group of foreign journalists in the North Korea capital, Pyongyang.
He would not comment on when the fuel injection would be complete. "And as for the exact timing of the launch, it will be decided by my superiors,'' Paek said.
Space consultant James Oberg asked, "When would we get the first radio signals from the satellite?" The director said the first radio signals would be received about 12 hours after launch.
Oberg told NBC News that he had plotted the orbit of the satellite and said it would not really come directly over North Korea for about 11 or 12 hours. However, radio amateurs outside North Korea have a much better opportunity to pick up signals from the satellite beginning in western Australia 20 minutes after launch. The U.S. eastern seaboard would be able to hear it in the following hour.
The director said the satellite would be broadcasting North Korean songs celebrating the "Dear Leader" and encouraged people around the world to tune in and listen.
Regional powers said the launch is a disguised test of the North's long-range missile.
South Korea, which remains technically at war with the North after their 1950-53 conflict ended with a truce rather than a peace treaty, warned Pyongyang it would deepen its isolation if it went ahead with the launch.
Security sources in Seoul, citing satellite images, have said that North Korea, which walked out of "six-party'' disarmament talks three years ago, is also preparing a third nuclear test following the launch, something it did in 2009, and a move bound to trigger further condemnation and isolation.
U.S. Secretary of State Hillary Clinton warned that history pointed to "additional provocations" from North Korea after the launch, apparently a reference to a nuclear test.
"This launch will give credence to the view that North Korean leaders see improved relations with the outside world as a threat to their system,'' she told cadets at the U.S. Naval Academy in Annapolis, Maryland.
"And recent history strongly suggests that additional provocations may follow."
She also called on China to do more to ensure regional stability.
China, impoverished North Korea's only major ally, on Tuesday reiterated its pleas for calm and said it had "repeatedly expressed its concern and anxiety about the developments," Foreign Ministry spokesman Liu Weimin told a press briefing in Beijing.
NBC News' Ed Flanagan and Reuters contributed to this report.
More from msnbc.com and NBC News:
- F-1 cars to race amid deadly Bahrain crackdown?
- F-15s scrambled as 'credible bomb threat' diverts jetliner
- 'Jackie Kennedy of China' suspected in death of British businessman
- Hook-handed radical Muslim Abu Hamza can be sent to US, court rules
- N.Koreas 'unconvincing' answers to satellite questions
- Amid Iran tensions, neighbor becomes den of spies
- When the Olympics is your neighbor
Follow us on Twitter: @msnbc_world