Defying worldwide calls to back down, North Korea said Wednesday it is fuelling a rocket for launch during a landmark anniversary as it gave its young leader a new title to bolster his authority.

Pyongyang has scheduled the launch in a five-day window starting Thursday. It says the "historic" event is a centrepiece of celebrations marking the 100th anniversary of the birth of founding leader Kim Il-Sung on April 15.

The rocket is ostensibly designed to put an observation satellite in orbit, but the United States and allies say it is in fact a ballistic missile test by the nuclear-armed state in violation of a United Nations ban.

The anniversary will celebrate the family dynasty which has ruled the impoverished nation since 1948 and cement the power of the founder's grandson Kim Jong-Un, who took over after his own father Kim Jong-Il died in December.

The ruling Workers' Party, holding only its fourth-ever special conference Wednesday, conferred an apparently new title of "first secretary" on Jong-Un and declared his late father its "eternal" general secretary.

"The communist state has created the new title for Jong-Un to control the party while continuing the legacy of his father," Cheong Seong-Chang of South Korea's Sejong Institute told AFP.

Paik Hak-Soon of the same institute said the decision was "rather a smart move... to highlight Jong-Un's loyalty and love for his father and thus further legitimise his status as the latest protege of the ruling Kim dynasty".

In Pyongyang, officials said launch preparations were proceeding apace.

"We are injecting fuel as we speak. It has started (and it) will be over in the near future," Paek Chang-Ho, director of North Korea's mission control centre just outside Pyongyang, told foreign journalists.

"The launch of the satellite this time will be successful because Comrade Kim Jong-Un is guiding us through the launch step by step, and gives us personal guidance," he said.

The same mission control was used when North Korea last said it placed a satellite in orbit, in 2009. Foreign experts said no satellite was detected in orbit and called that exercise a disguised ballistic missile test.

The 2009 launch was followed by a nuclear test, and the West fears the same pattern is being repeated now as the communist state tries to perfect dual-use technology that can double for intercontinental missiles.

US Secretary of State Hillary Clinton on Wednesday said that the Group of Eight industrialised powers had a "strong interest" in seeking stability on the Korean peninsula, as she reiterated that the launch "violates multiple UN resolutions".

Admiral Samuel Locklear, the head of the US Pacific Command, said in Tokyo Wednesday that North Korea over time has pursued "increasingly sophisticated ballistic missile defence technologies".

If the nation can increase the potential range of its missiles, this "will be a concern for the alliance, a concern for the region as well as a concern for the United States", he said.

Germany Wednesday was the latest nation to try to persuade the North to call off the launch, saying it would be a "clear provocation".

However, North Korea insists it has nothing to hide and has invited an unprecedented number of foreign journalists to cover the commemorations.

Four busloads of visitors were escorted to the two-storey mission control in a heavily guarded, wooded compound in Pyongyang's northern suburbs. Inside were 16 white-coated technicians, both men and women, hunched over computer screens.

A main screen showed what official minders said was a live image of the 30-metre (100-foot) rocket on its launchpad in the country's far northwest, shrouded at its top to protect the satellite payload.

North Korea has rejected criticism that the launch of the Unha-3 (Galaxy 3) rocket could feed its hungry people for a year.

Before the anniversary, tens of thousands in the tightly regimented state have been sprucing up the capital Pyongyang as the government's propaganda machine rallies the people behind Kim Jong-Un, who is in his late 20s.

An annual session of parliament will be held Friday. Legislators could elevate him to his father's old post, chairman of the all-powerful National Defence Commission.

North Korea also announced Wednesday the appointment of a new armed forces minister, Kim Jong-Gak, in what analysts said was a sign the new leader is installing close confidants to key posts.

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