North Korea has completed installing a long-range rocket on its launch pad, ahead of its planned launch this month in defiance of widespread international condemnation, a report said Wednesday.

All three stages of the Unha-3 rocket have been placed on the pad at the North's Sohae satellite launch station, a South Korean government source told Yonhap news agency.

"Some workers are pulling out of the site," the source said.

Pyongyang announced on Saturday that it intends to launch the rocket between December 10 and 22.

The United States and its key Asian allies South Korea and Japan have condemned the move as a disguised ballistic missile test that violates UN resolutions triggered by Pyongyang's two nuclear tests in 2006 and 2009.

North Korea is now expected to install support equipment, such as radar and cameras, before fueling the carrier, Yonhap said.

US Secretary of State Hillary Clinton on Tuesday urged her NATO allies and Russia to press North Korea to call off the mission.

"The United States is deeply concerned about North Korea's recent announcement that it plans to carry out another rocket launch," Clinton told a meeting of the NATO-Russia council.

"We urge everyone here to publicly call upon North Korea to comply fully with its UN Security Council obligations."

Pyongyang insists the launch is a "peaceful" and purely scientific mission aimed at placing a satellite in orbit.

A previous attempt in April failed when the carrier exploded shortly after take-off.

China has expressed "concern" at the launch plan, with the foreign ministry urging "relevant parties (to) act in a way that is more conducive to the stability of the Korean peninsula".

Russia added its "regret" and noted that North Korea was obliged to abide by UN resolutions.

But analysts say the international community is running out of options for pressuring the impoverished but nuclear-armed North, which is already under layers of sanctions.

The six-party, aid-for-denuclearisation talks have been at a standstill since Pyongyang walked of the forum in April 2009. It staged its second nuclear test a month later.