New satellite images of the launch site appear to show a mobile radar trailer and rows of empty fuel tanks. Experts say the pictures provide evidence that North Korea's work on the launch is going according to schedule.
The launch is set for sometime between April 12 and 16.
North Korea says its launching a satellite, but the U.S. and others say the country is testing missile systems for nuclear weapons.
Discussions of the launch were expected to dominate the Association of Southeast Asian Nations annual diplomatic summit, which starts Tuesday.
The Associated Press contributed to this report.