North Korea urged its people Sunday to defend new leader Kim Jong-Un to the death and vowed an all-out push for prosperity, in a New Year state newspaper editorial setting out policy goals.

"The whole party, the entire army and all the people should possess a firm conviction that they will become human bulwarks and human shields in defending Kim Jong-Un unto death, and follow the great party for ever," it said.

Jong-Un, aged in his late 20s, was proclaimed the "great successor" after his father and longtime leader Kim Jong-Il died on December 17.

On Saturday the North announced he had formally been appointed supreme commander of the 1.2-million-strong military, the world's fourth-largest.

Chinese President Hu Jintao, whose country is the North's main ally and economic prop, sent Jong-Un "warm congratulations" on assuming the military leadership, the North's official news agency said Sunday.

The North, closing ranks publicly behind its new chief, has warned the world not to expect policy changes and has threatened South Korea for perceived disrespect during the 13-day mourning period for Kim Jong-Il.

Sunday's editorial vowed to "consolidate" the armed forces and called for the United States to pull its 28,500 troops out of South Korea. But it said Pyongyang will "strive to develop relations of friendship with countries that respect our country's sovereignty".

The editorial, published in the ruling communist party newspaper Rodong Sinmun and other papers, stressed the role of the party, which was sidelined by Kim senior in favour of the military.

"To achieve victory in (the) general advance for this year it is necessary to strengthen the party and enhance its leadership role to the maximum," it said.

The impoverished country has set the goal of becoming a "powerful and prosperous" nation this year. April 15 marks the 100th anniversary of the birth of late founding president Kim Il-Sung, grandfather of the current leader.

"This year is the year when Kim Jong-Il's plan for achieving prosperity will bear a brilliant fruit," the editorial said, calling for "an all-out drive to implement our party's grand strategy for achieving prosperity".

The editorial, used every year to outline the policy agenda, did not mention the country's nuclear weapons programme, which has earned it international sanctions.

The North has expressed willingness in principle to return to six-country nuclear disarmament talks but the United States says it must first take steps to show its sincerity.

The editorial renewed criticism of the South's conservative government, saying the "traitors" failed to respect the mourning for Kim.

Seoul expressed sympathy to the North's people but not its regime and allowed just two private mourning delegations to visit Pyongyang.

As in most years, the editorial laid stress on the need to develop light industry and called for innovations in basic industries.

The North's economy shrank in 2010 for the second straight year, South Korea's central bank has estimated. Factories grapple with serious shortages of electricity and raw materials.

Outside the showpiece capital Pyongyang, millions face a daily struggle just to feed themselves and their families. Famine which began in the mid-1990s killed hundreds of thousands and severe food shortages persist.

Per capita gross domestic product, by most estimates, is now 1/19th the size of the South.

The editorial acknowledged that the food problem is a "burning issue" and called for efforts to solve it.

However, it stressed no deviation from policies set by the late leader and also called for an intense struggle against "imperialists' ideological and cultural infiltration".