"The North Koreans will be violating [U.N.] Security Council resolutions if they move ahead with such a launch," George Little, acting assistant secretary of defense for public affairs, told reporters, "and we call on them, as other countries have, not to launch the missile."
North Korea announced last month it would launch a long-range Unha-3 rocket between April 12 and April 16. Koran officials said the rocket would carry a North Korean-made observation satellite to mark the 100th birthday of the late President Kim Il Sung April 15.
Western countries, however, said they believe the launch is really a test-firing of a missile.
"This is very serious business when North Korea does something like this," Little said. "We're monitoring it closely. We understand the impact it could have on regional stability."
Little said the United States would work with regional allies to monitor the situation.
"We hope it doesn't happen," he said. "But if it does, we'll be ready to track it."