South Korea's nuclear envoy headed to Washington on Friday for talks with US officials as regional powers scrambled to coordinate a joint strategy for North Korea's planned rocket launch.

North Korea says it will send a communications satellite into orbit between April 4 and 8 as part of a peaceful bid to develop its space program.

But some governments suspect the North will use the launch to test the delivery technology for a long-range missile capable of striking Alaska - or may even fire off missile itself.

The US, South Korea, Japan and other nations denounced the launch as a provocative move banned under a 2006 U.N. Security Council resolution prohibiting ballistic activity, and have warned it would invite international sanctions.

Moscow joined calls for Pyongyong to cancel the launch.

"We would like to stress that there is no need to heighten tensions," Russian news agencies quoted deputy Foreign Minister Alexei Borodavkin as saying Friday.

With the rocket now on the launchpad in Musudan-ni in the northeast, North Korea is technically prepared to launch it as early as Saturday, South Korea's Chosun Ilbo newspaper said, citing an unnamed diplomatic official.

In Tokyo, Japanese Defense Minister Yasukazu Hamada ordered the military to prepare to shoot down any debris that could fall on Japanese territory if the rocket launch fails. He called on troops to mobilize interceptor missiles and has sent two warships to the Sea of Japan.

South Korea is also dispatching an Aegis-equipped Sejong the Great destroyer off the east coast to monitor the launch, a military official in Seoul said. He asked not to be named because he was not authorized to speak to the media.

The 7,600-ton destroyer can detect and track targets hundreds of miles (kilometers) away, the military says.

Two US Aegis-equipped ships, docked in South Korea, will set sail in coming days, US military spokesman Kim Yong-kyu said.

In Washington, envoy Wi Sung-lac plans to meet President Barack Obama's envoys on North Korea, Stephen Bosworth and Sung Kim as well as with Japan's nuclear envoy, Akitaka Saiki, who will also be in Washington, South Korea's Foreign Ministry.

"As North Korea's rocket launch preparations gather pace, I will have consultations on the issue and the six-way talks" on dismantling the North's nuclear program, Wi told reporters before his departure.