The United States voiced doubt Friday over whether it could move ahead with providing food aid to North Korea if the isolated Asian nation follows through on its threat to launch a long-range rocket.

"Were we to have a launch, it would create obviously tensions and that would make the implementation of any kind of nutritional agreement quite difficult," State Department spokeswoman Victoria Nuland said.

"It's very hard to imagine how we would be able to move forward with a regime whose word we have no confidence in and who has egregiously violated its international" obligations, Nuland told reporters.

On February 29 the United States said it would move ahead on a plan to deliver 240,000 metric tons of food aid to Pyongyang after North Korea agreed to halt its nuclear program and missile launches and allow back UN inspectors.

Nuland said that US diplomats told their North Korean counterparts prior to the February 29 agreement that a missile launch would be a "deal breaker."

Before dawn in Washington, Nuland issued a statement calling the proposed launch "highly provocative" and a threat to regional security, saying it would breach a United Nations ban imposed after previous launches.

The statement was issued just hours after North Korea announced it would launch a long-range rocket next month to put a satellite into orbit -- something Nuland said was so serious that a quick US response was required.

"We wanted to make absolutely clear what our views were with regard to it without much time passing from the release of their statement," Nuland said.