North Korea has vowed to stage an all-out drive for prosperity and unite behind new leader Kim Jong-un, ushering in 2012 with promises to resolve food shortages, bolster its military and defend Kim Jong-il's young son "unto death".

The pledge in North Korea's annual new year message comes as the country enters a new era, with Kim Jong-un installed as supreme commander of the 1.2 million-strong military and ruling party leader following his father's death.

The message did not include the north's routine harsh criticism of the US and avoided the country's nuclear ambitions, a suggestion that Pyongyang is willing to continue talks with Washington to win food aid.

This year is a crucial one for North Korea as it tries to build a "great, prosperous and powerful nation" befitting the April 2012 centenary of the birth of national founder Kim Il-sung, the new leader's grandfather.

"Glorify this year 2012 as a year of proud victory, a year when an era of prosperity is unfolding," said the message, carried by the official Korean Central News Agency. "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."

North Korea said it would boost its military, and boasted that it was "at the epochal point of opening the gates of a thriving country" with parts of Pyongyang "turned into socialist fairylands".

The message acknowledged the country's food crisis, saying "the food problem is a burning issue". North Korea had been in talks with the US on food aid, but they stopped because of Kim Jong-il's death.

The United Nations has said a quarter of North Korea's 24 million people need outside food aid and that malnutrition is surging, especially among children.

The new year message said organic farming methods should be used and that farming machinery and materials should be provided, but did not go into specifics for improving food supplies.

The message, a joint editorial appearing in the Rodong Sinmun, Joson Inmingun and Chongnyon Jonwi newspapers, said North Korea must build on foundations laid last year and turn itself "into an economic giant". It also stressed the need to boost its power and coal industries and promote studies of information technology and bioengineering.

"This year's message shows North Korea will focus on its economy and ideological solidarity to establish stability," said Yoo Ho-yeol, a professor at Korea University in South Korea.

"There is also no specific mention of the United States or the nuclear programme, and that shows North Korea is leaving room for the chance of improved ties with the United States," Yoo said.The message spoke of a desire for reunification with South Korea – a point North Korea often mentions – but did not give specifics. The north warned on Friday that there would be no softening of its position toward South Korea's government after Kim Jong-il's death.

North Korea, which has tested two atomic devices since 2006, has said it wants to return to long-stalled talks on halting its nuclear weapons programme in return for aid. Washington and Seoul, however, have insisted that the north shows progress on past disarmament commitments before negotiations can resume.

The six-nation talks involve the two Koreas, the US, China, Russia and Japan.

The Korean peninsula remains technically in a state of conflict because the 1950-53 Korean war ended in a truce, not a peace treaty.

Kim Jong-un also received a boost from China, his country's biggest backer. President Hu Jintao sent congratulations to Kim late on Saturday on his appointment as supreme military leader. The message, carried on the government's website, was China's most direct show of support for the new leader. It said the people and armies of the countries had a deep traditional friendship, and that relations would continue to be strengthened.