The United States warned Friday it would not send food aid to North Korea if it goes ahead with a rocket launch next month.
State Department spokeswoman Victoria Nuland said the U.S. now has "grave concerns" about the Feb. 29 agreement that had eased tensions between the long-term adversaries.
Under the accord, Pyongyang agreed to nuclear concessions and a moratorium on long-range missile tests in return for 240,000 tons of American food aid for the impoverished country.
In a surprise announcement, North Korea said Friday it plans to launch a satellite into space on the back of a long-range rocket between April 12 and 16 off its west coast _ a provocative step just as its new leader Kim Jong Un consolidates his power.
The U.S., South Korea and other critics say the rocket technology overlaps with belligerent uses and condemn the satellite program as a disguised way of testing military missiles in defiance of a U.N. ban.
Nuland told a news briefing that a rocket launch would call into question North Korea's good faith and would not create an appropriate environment to go ahead with the food shipments.
"We did warn them (North Korea) that we considered that a satellite launch of this kind would be an abrogation of that agreement," Nuland said.
Under the agreement, the North also agreed to allow in inspectors from the U.N. International Atomic Energy Agency, which have not been able to monitor the North's expanding nuclear program for three years.
Friday's announcement by the North also will set back prospects for resumption of six-nation aid-for-disarmament talks that the North withdrew from in 2009.
The Obama administration says it is offering the food aid for humanitarian reasons and denies it is in exchange for the North Korean concessions, a position that may appear less believable if the U.S. now refuses to go ahead with the shipments.
Nuland, however, said a launch would cast doubt on the North's commitment to allow effective monitoring of food distribution, which is intended to prevent diversion of aid from the needy to "regime elites."
Nuland said the U.S. envoy on North Korea, Glyn Davies, spoke overnight to six-party talks counterparts from China, Japan, Russia and South Korea, and they all agreed to "use their influence" to encourage the North to stick to the Feb. 29 agreement.
"We all need to encourage them to change course," she said.
At the U.S. Department of Defense, spokesman Navy Capt. John Kirby said a launch would be a "very clear violation" of U.N. resolutions and of North Korea's international obligations.
"We would consider it destabilizing behavior," and the U.S. would like North Korea's leaders to reconsider their decision, Kirby said.
The U.S. retains 28,000 troops in South Korea, a legacy of the 1950-53 Korean War that ended without a peace treaty.
Associated Press writer Robert Burns contributed to this report.