South Korea has warned the North it will "pay a harsh price" if it goes ahead with its plan to launch a satellite into space.
North Korea said on Tuesday it intended to carry out the launch between 8 and 25 February.
Critics say it is a cover for a test of ballistic missile technology.
Washington has said it would be an "egregious violation" of a UN ban on missile launches by North Korea, and called for more sanctions.
North Korea has always said its space programme is peaceful, but it is believed to be developing an intercontinental ballistic missile.
It also conducted its fourth nuclear bomb test on 6 January, drawing international condemnation.
Cho Tae-yang, a senior South Korean presidential official, said on Wednesday that the satellite plan was considered a "direct challenge to the international community".
"We warn that if North Korea proceeds with a long-range missile launch, the international society will ensure that the North pays searing consequences for it as the launch would constitute a grave threat to the Korean Peninsula, the region and the world," he said.
Japan's Prime Minister Shinzo Abe said the launch plan was a "serious provocation" and that he would work with other countries to "strongly demand" North Korea to stop.
China's top nuclear envoy Wu Dawei, is currently visiting Pyongyang. A Chinese foreign ministry official told the South Korea news agency Yonhap that he planned to discuss the situation with officials there.
The International Maritime Organization (IMO) says on Tuesday that it had been notified of Pyongyang's plans to launch a satellite between 8 and 25 February.
However North Korean media do not appear to have reported on the DPRK's letter to the UN maritime agency so far, says BBC Monitoring, meaning many North Koreans will not be aware of it.
US Assistant Secretary of State for East Asia Daniel Russel said the planned launch argued "even more strongly" for tougher UN sanctions.
Analysts say a new launch would allow North Korea to test some - but not all - of the technology needed for a long-range nuclear strike.
US officials had said last week that North Korea appeared to be preparing for a rocket launch, citing increased activity around the Sohae Satellite Launching Station, also known as Tongchang-ri.
Analysts say that the recent activity could be a build-up to the seventh Congress of the Workers' Party of Korea due to be held in coming months, the first to be held since 1980, where leader Kim Jong-un is expected to show off North Korea's nuclear programme.
The North last conducted a long-range rocket launch in December 2012, successfully putting into orbit an object Pyongyang claimed was a communications satellite with the three-stage Unha-3 carrier.
The UN Security Council subsequently called it a "clear violation" of resolutions banning North Korea from missiles tests, and imposed sanctions, foreign media reports.