WASHINGTON (AP) _ A long-range rocket launch planned by North Korea probably would wreck its recent food-for-nuclear concessions agreement with the United States and, with it, hopes for improving relations under the North's new leader, Kim Jong Un.

   The North announced Friday its planned launch of a satellite into space, marking a sharp and sudden turn just 17 days after the two countries offered unexpected signs of hope that three years of tensions were easing. Such a launch would violate a U.N. ban.

   ``It's a real slap in the face,'' said Victor Cha, a White House director for Asia policy during the George W. Bush administration. ``It undercuts a lot of theories that the young leadership might be different. If anything, it shows that it's very much the same as before, only more unpredictable.''

   It is an embarrassment in an election year for President Barack Obama, who has been accused by Republican presidential candidates as naive in his foreign policy. Republican lawmakers already have criticized his administration for ``appeasing'' Pyongyang by offering 240,000 tons (217,725 metric tons) of food in exchange for a freeze on nuclear activities and a moratorium on nuclear and long-range missile tests.

   If North Korea carries out the launch, it will be hard to keep alive the accord announced Feb. 29. State Department spokeswoman Victoria Nuland said Friday that a satellite launch would be a ``deal-breaker'' and indicated that the United States would be very unlikely to send the food notwithstanding what Washington says are the purely humanitarian reasons for offering to feed malnourished North Koreans. She explained that a launch in abrogation of the North's commitments would undermine confidence that the North would allow proper monitoring of the distribution of the aid.

   The North's announcement highlights the pitfalls of negotiating with a secretive regime, which views its nuclear program as a deterrent against invasion. The United States retains 28,000 troops in South Korea, a legacy of the 1950-53 Korean War, and the two Koreas remain in a state of war as the conflict ended without a peace treaty.

   Previous U.S. efforts over the past two decades to persuade North Korea to disarm always have ended in disappointment. Even before Friday's announcement, a group of five Republican senators wrote to Secretary of State Hillary Rodham Clinton this week accusing the administration of accepting the North's ``hollow commitments.''

   Although North Korea says the rocket launch will be for peaceful means, the same kind of technology is used for ballistic missiles, which could eventually provide a delivery system for a nuclear weapon if the North should become able to miniaturize one for use on a warhead.

   ``They (North Korea) are putting the Obama administration in a very, very difficult position,'' said Evans Revere, a former senior State Department official for East Asia. ``The administration would have little choice but to react in a firm way to this.''

   The United States could refer the matter to the U.N. Security Council. The last time North Korea conducted such a rocket launch, in April 2009 _ also described as a bid to send a communications satellite into space _ the council condemned it.

   Whether permanent council members Russia and China, the North's closest ally, would support such a step this time remains unclear. All parties will be mindful of what can happen if the North feels cornered. Soon after the 2009 launch, the North conducted a nuclear test.

   For now, the U.S. says it is consulting with the other parties in suspended six-nation disarmament talks to encourage the North not to go ahead with the launch. The North says it plans to conduct the launch between April 12 and 16, in commemoration of the centennial of the birth of its founder, Kim Il Sung, the new leader's grandfather.

   That the North is prepared to take that step, risking international censure and spoiling its diplomatic outreach to Washington, underscores the importance of the centennial, as the untested Kim Jong Un seeks to consolidate his power. It also would fuel speculation over the internal dynamics in the new government and whether it has competing policy aims.

   A major international nuclear summit in South Korea March 26-27, to be attended by Obama, will provide a high-profile opportunity for the international community to crank up diplomatic pressure on the North over its plans, although most analysts doubt it will change course.

   ``The U.S. will probably really lean on the Chinese,'' said Jonathan Pollack, an expert on North Korea's nuclear program at the Brookings Institution think tank. He said he expected the message to China to be: ``You remember what happened last time they tried to launch a satellite?''