Reclusive North Korea has said it is merely sending a weather satellite into space, but South Korea and the United States say it is a disguised ballistic missile test.
North Korea said on Tuesday there was no reason to fire a missile after February's agreement to suspend nuclear and missile tests in return for food aid with the United States.
But Acting Assistant Secretary of Defense for Asia and Pacific Security Affairs Peter Lavoy told the House of Representative Armed Services Committee that the announcement of the launch was in breach of the February agreement.
"This planned launch is highly provocative because it manifests North Korea's desire to test and expand its long-range missile capability," Lavoy told the House panel.
"We believe this reflects their lack of desire to follow through on their commitments, their international commitments, and so we've ... been forced to suspend our activities to provide nutritional assistance to North Korea." A US official confirmed the United States had detected activity that looked like launch preparations at a facility near the country's northwestern border with China.
The launch, which even drew criticism from ally China, will mark the 100th birth anniversary of state founder Kim Il-sung.
The website GlobalSecurity.org published satellite imagery last week of a launch pad and tower without a rocket at the Tongchang-dong launch site. A US official indicated there were signs the North Koreans were getting the site ready.
"The US has seen indications that the North Koreans are preparing to launch a long-range rocket," said the official.
Pentagon spokeswoman Leslie Hull-Ryde said the United States and South Korea were monitoring North Korea, but declined to comment on specific intelligence on the launch.
North Korea, which three years ago pulled out of on-again-off-again six-party talks on reining in its nuclear program, has said the rocket will travel south toward the Philippines or Indonesia, Lavoy told US lawmakers.
US military officials told the House panel the North's large conventional military, nuclear weapons programs, ballistic missiles and newer capabilities in cyber warfare all threatened the United States and its allies in the Asia-Pacific region.
North Korea has added sophisticated cyber attack capabilities to its arsenal of threatening weapons and this year was rife with opportunities for military provocations from Pyongyang, beginning with the rocket launch next month, the US defense officials said on Wednesday.
