White House press secretary Jay Carney, speaking to reporters aboard Air Force One en route to West Palm Beach, Fla., said, "The proposed missile launch, if conducted, would represent a clear and serious violation of North Korea's obligations under two United Nations Security Council resolutions that explicitly prohibit North Korea from testing ballistic missiles."
Carney said the United States "will continue to work with ... our partners on next steps if North Korea goes through with this provocation."
In response to a question, Carney said U.S. food aid might be cut off from the North Korean regime.
"We've said explicitly that it's impossible to imagine that we would be able to follow through with our ... nutritional assistance that we had planned on providing, given what would be a flagrant violation of ... North Korea's basic international obligations.
"Beyond that ... I don't have any information for you. We'll consult with our allies and partners."
The rocket North Korea is preparing to launch appears to be a more advanced version of one fired in April 2009, South Korean scientists said.
North Korea allowed foreign journalists to glimpse the rocket sitting on its launch pad in the country's northwest, near the Chinese border.
South's Korea Aerospace Research Institute said the rocket is slightly more advanced than the 2009 version and is likely to have a better booster, the Chosun Ilbo reported Tuesday.
In the 2009 launch, the rocket's second- and third-stage boosters successfully separated but failed to put a satellite into orbit, possibly because of a lack of thrust, a South Korean space official told the newspaper.
North Korea has adamantly denied international claims the rocket launch is a cover for a testing an intercontinental missile capable of carrying nuclear weapons.
Ryu Gum Chol, an official with the Korean Committee for Space Technology in North Korea, said the Kwangmyongsong-3 satellite will be installed on the Unha-3 carrier rocket Tuesday.
He said the 91-ton, three-stage rocket doesn't have the same "attack power" as a ballistic missile, China's official Xinhua News Agency reported.
Ryu said foreign journalists would be invited Wednesday to visit the space control center in Pyongyang.