Kim Jong-un, the North Korean leader, has vowed to take "substantial and high-profile important state measures” and ordered his top military and party officials of what to do to retaliate against American-led United Nations sanctions on the country, the North’s official media reported on Sunday. North Korea did not clarify what those measures might be, but it referred to a series of earlier statements in which Mr. Kim’s government has threatened to launch more long-range rockets and conduct a third nuclear test to build an ability to "target” the United States. Mr. Kim threw his weight behind his government’s escalating standoff with Washington when he called a meeting of top security and foreign affairs officials and gave an instruction in his name. He inherited the supreme party and military leadership from his father, Kim Jong-il, who died in December 2011. By calling such a meeting and having it reported in state news media, Mr. Kim seemed to assert his leadership in what his country called an "all-out action” against the United States, as opposed to his father, who tended to remain reclusive during similar confrontations. "At the consultative meeting, Kim Jong-un expressed the firm resolution to take substantial and high-profile important state measures in view of the prevailing situation,” said the North’s Korean Central News Agency, or K.C.N.A. "He advanced specific tasks to the officials concerned.” The K.C.N.A. dispatch, which was distributed on Sunday, was dated Saturday, indicating that the meeting in Pyongyang took place then. That was the same day on which the North’s main party newspaper, Rodong Sinmun, said that the United Nations Security Council’s resolution last Tuesday calling for tightening sanctions against the North left it with "no other option” but a nuclear test. "A nuclear test is what the people demand,” it said in a commentary. The resolution was adopted unanimously — with the support of the North’s traditional protector, China — as punishment for its Dec. 12 rocket launching. The Security Council determined that the launching was a cover for testing intercontinental ballistic missile technology and a violation of its earlier resolutions banning North Korea from such tests. The North rejected the old resolutions, as well as the latest, insisting that launching rockets to put satellites into orbit was its sovereign right. Its successful rocket launching in December, coming after a failure last April, was the most visible achievement Mr. Kim’s government could present for its people, who have suffered decades of poverty and isolation. In North Korean propaganda, defending its rocket program is likened to protecting national pride and independence — even if it has to pay economic prices. Last Thursday, North Korea said that its drive to rebuild its moribund economy and its rocket program, until now billed as a peaceful space project, would be adjusted into efforts to foil United States hostilities.  On Sunday, it said the Security Council’s action "has thrown a grave obstacle” to its efforts to focus on "economic construction so that the people may not tighten their belts any longer.” Still, it said it had to "defend its sovereignty by itself” because "different countries concerned” failed to "fairly solve the problem.” In the past few days, North Korea, without citing China by name, expressed bitterness and defiance against its long-time Communist ally for endorsing the American-led Security Council resolution. On Saturday, Rodong reaffirmed its dislike of "sadae,” or toadying big countries, including China. Agencies