“North Korea’s notice of the plan to launch a long-range missile, coming at a time when there is a discussion for Security Council sanctions on its fourth nuclear test, is a direct challenge to the international community,” the Blue House said.

“We strongly warn that the North will pay a severe price ... if it goes ahead with the long-range missile launch plan,” it said.

Japanese Prime Minister Shinzo Abe said he would work with the United States and others to “strongly demand” that North Korea refrain from what he described as a planned missile launch.

Japan’s Defence Minister Gen Nakatani ordered ballistic missile defence units including Aegis destroyers in the Sea of Japan (East Sea) and Patriot missile batteries onshore to be ready to shoot down any North Korean rocket that threatened Japan.

The rocket is likely to fly over Japan’s southern island of Okinawa in the Pacific Ocean at an altitude of several hundred kilometres.

Reports of the planned launch drew fresh US calls for tougher UN sanctions that are already under discussion in response to North Korea’s recent nuclear test.

State Department spokesman John Kirby said the United Nations needed to “send the North Koreans a swift, firm message”.

But China’s Foreign Ministry spokesman Lu Kang expressed scepticism over calls by the US for tough new sanctions.

“We hope all sides show restraint and take prudent action to avoid any moves that may increase the tensions on the (Korean) Peninsula,” Lu told reporters at a regularly scheduled news briefing.

Lu’s comments come as US diplomats are urging China to use its political and economic influence with North Korea to compel it to stop such actions.

China has pushed back against US calls for tougher sanctions. Foreign Minister Wang Yi argued during a visit last week by US Secretary of State John Kerry that sanctions are not an end unto themselves and any new UN resolution should not provoke new tensions.

North Korea’s announcement came during a visit to Pyongyang by China’s top envoy to North Korea, Wu Dawei. That could be seen as a snub to Beijing, North Korea’s most important ally which, nevertheless, has been unable to restrain Pyongyang’s actions.

Lu said only that Wu was in Pyongyang for the purpose of “exchanging views with the North Korea side over the current situation

Pyongyang has said it has a sovereign right to pursue a space programme by launching rockets, although the United States and other governments worry that such launches are missile tests in disguise.

A spokeswoman for the International Maritime Organisation, a UN agency, said the agency had been told by North Korea it planned to launch the ‘Kwangmyongsong’ satellite.

The International Telecommunication Union, another UN agency, also said that North Korea had informed it on Tuesday of plans to launch a satellite with a functional duration of four years in a non-geostationary orbit.

North Korea said the launch would be conducted in the morning one day during the announced period, and notified the coordinates for the locations where the rocket boosters and the cover for the payload would drop.

Those locations are expected to be in the Yellow Sea off the Korean peninsula west coast and in the Pacific Ocean to the east of the Philippines, Pyongyang said.

US officials said last week North Korea was believed to be making preparations for a test launch of a long-range rocket, after activity at its test site was observed by satellite.

North Korea last launched a long-range rocket in December 2012, sending an object it described as a communications satellite into orbit.

North Korea also said last month it had successfully tested a hydrogen bomb but this was met with scepticism by U.S. and South Korean officials and nuclear experts. They said the blast was too small for it to have been a full-fledged hydrogen bomb.

Additional reporting by Associated Press