PYONGYANG, North Korea - North Korea has officially named Kim Jong Un as Supreme Commander, the country said Saturday, putting him formally at the head of the 1.2-million-strong military and further strengthening his authority after Kim Jong Il's death.

An unannounced Workers' Party meeting Friday proclaimed that Kim Jong Il's son and successor, who is in his late 20s, "assumed supreme commandership of the Korean People's Army" according to a will made by Kim Jong Il on Oct. 8, the North's official Korean Central News Agency said.

The meeting of the ruling party came one day after the official mourning period for Kim Jong Il ended and senior military and political officials publicly declared Kim Jong Un leader of the party, military, and people. Officials and state media have bestowed a string of titles on him as North Korea's elite rally around him.

But the title Supreme Commander - and its formal approval by the powerful Political Bureau of the Central Committee of the Workers' Party - is a clear sign that Kim Jong Un is fast consolidating power over North Korea. It is also the latest incremental step in a burgeoning personality cult around him.

Kim Jong Un should be "the only center of unity, cohesion, and leadership" of the Workers' Party, state media said, and the military should uphold the songun, or military-first, politics laid down by Kim Jong Il.

Titles are an important part of North Korea's efforts to link Kim Jong Un to the myth-building surrounding the Kim family legacy.

Kim Il Sung, the country's first and only president, retains the title Eternal President even after his death.

Kim Jong Il held three main positions: chairman of the National Defense Commission, general secretary of the Workers' Party, and supreme commander of the Korean People's Army. According to the constitution, his position as chairman of the National Defense Commission made him Supreme Leader of North Korea.

Kim Jong Un was made a four-star general last year and appointed a vice chairman of the Central Military Commission of the Workers' Party. Since his father's death, he had already racked up major titles: Great Successor, Supreme Leader, and Great Leader earlier Friday.

Kim Jong Un's age and inexperience have raised questions outside North Korea about his leadership of a nation engaged in negotiations over its nuclear program and grappling with decades of economic hardship.

The North warned Friday that there would be no softening of its position toward South Korea's government.

North Korea's powerful National Defense Commission said the country would never deal with South Korean President Lee Myung Bak, a conservative who ended a no-strings-attached aid policy toward the North in 2008.

"We declare solemnly and confidently that the foolish politicians around the world, including the puppet group in South Korea, should not expect any change from us," the commission said.