North Korea on Friday warned South Korean leaders and other “foolish politicians” that its behavior would not soften under the untested leadership of Kim Jong Eun, youngest son and heir of the late autocrat Kim Jong Il.

Pyongyang excoriated South Korean President Lee Myung-bak and accused his government of hoping to use Kim Jong Il’s recent death to spur “system change.”

“Taking this opportunity,” North Korea said, “we solemnly declare with confidence that the south Korean puppets and foolish politicians around the world should not expect any change from the DPRK,” or Democratic People’s Republic of Korea.

With its first formal policy message since the elevation of Kim Jong Eun as supreme leader, North Korea indicated that it will navigate this latest transition by relying on a familiar strategy, using outside enemies to keep its people united.

The ongoing ascension of Kim Jong Eun has raised hopes among some outside analysts that the isolated nation will gradually reform, either opening its economy or dismantling its nuclear weapons. But Friday’s message reinforced a more pessimistic view, and Seoul’s Yonhap news agency said it “seems to represent Pyongyang’s future policy stance toward the South.”

“This is a message signaling the new Kim Jong Eun era,” said Jeong Young-tae, an analyst at the Seoul-based Korea Institute for National Unification. “Kim Jong Eun needs to grow up to be military leader. In order to do this, rhetoric creating tension and presenting confidence is needed.”

The 1,410-word statement was issued by the National Defense Commission, North Korea’s supreme policy-making body, and read by an anchorwoman on state television. It took aim mainly at Lee, the South Korean president who took office in 2008 and promptly cut off aid and economic cooperation deals instituted by more liberal predecessors.

The North on Friday accused Lee of “hideous crimes,” and named at least a half-dozen of them, including showing insufficient respect to Kim Jong Il by sending only a small and unofficial delegation to his funeral. It also criticized Lee for holding a state security meeting after Kim’s death and raising the alert level for troops.

“The south Korean puppets and world reactionaries should no longer make a fool of themselves in their bid to lead the DPRK to ‘contingency’ and make its ‘system unstable,’ something unimaginable,” the North said.

Some experts cautioned that the statement might prove to be mere posturing, not long-term policy. The North frequently threatens major military strikes against Seoul, and it has commonly called Lee a traitor. Tensions on the peninsula could also shift depending on the outcome of next year’s South Korean presidential election.

Since Kim Jong Il’s death, officials in Seoul and Washington have had little sense of who is running the country or how power is being shared. A backbone of elite generals and Workers’ Party members could support Kim Jong Eun’s ascension; they might also challenge it. And if the younger Kim does consolidate power, little is known about how he’ll wish to use it.

Just before Kim Jong Il’s death, Washington was nearing an announcement about a resumption of food aid to the North, with the possibility of Pyongyang agreeing to a freeze on its uranium enrichment program. There is no way to know whether North Korea will welcome that deal under its new leader.

“For a moment we will see some continuity in policy,” said Zhu Feng, a North Korea expert at the University of Peking, in Beijing. “It’s very important for the young leader and his regents to consolidate the power base. I don’t think for the time being Kim Jong Eun will rush to any change.”

Special correspondent Yoonjung Seo in Seoul contributed to this report.