South Korea has warned of "searing" consequences if North Korea does not abandon plans to launch a long-range rocket that critics call a banned test of ballistic missile technology.
South Korea's rhetoric about unspecified harsh consequences comes less than a month after North Korea's defiant fourth nuclear test and as diplomats at the UN work on strong new sanctions against the country.
North Korea informed international organisations of its plans to launch an Earth observation satellite on a rocket between February 8 and 25.
The launch declaration, which is meant to warn civilians, shipping and aircraft in the area about the rocket and falling debris, follows North Korea's disputed claim on January 6 to have tested a hydrogen bomb, the country's fourth nuclear test.
A launch would be seen as a snub by North Korea of its only major ally, China, whose representative for Korean affairs landed in the country for talks on Tuesday.
South Korean and US officials said the launch would threaten regional security and violate UN Security Council resolutions that ban the country from engaging in any ballistic activities.
"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," senior South Korean presidential official Cho Tae-yong said.
In Washington, Daniel Russel, the top diplomat for East Asia, said the US was tracking reports of North Korea's planned launch. He said a launch that uses ballistic missile technology would be another violation of a UN ban and strengthens the argument for the international community to impose "real consequences" on North Korea for destabilising behaviour. He called for the imposition of tough additional sanctions.
Mr Russel said a launch "would be an unmistakable slap in face to those who argue that you just need to show patience and dialogue with the North Koreans but not sanctions," in an apparent reference to China.
China urged all sides to show restraint over North Korea's announcement of its launch plans, and expressed scepticism over the US calls 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," Chinese foreign ministry spokesman Lu Kang told reporters at a regularly scheduled news briefing.
North Korea has spent decades trying to develop operational nuclear weapons along with missiles capable of striking the mainland United States.
North Korea's last long-range rocket launch, in December 2012, was seen as having successfully put the country's first satellite into orbit after a string of failures. North Korea also told international agencies before that launch of its plans.
Each new rocket launch improves North Korea's missile technology, which is crucial for its goal of developing a nuclear-armed missile capable of hitting the US mainland.
UN deputy spokesman Farhan Haq said North Korea informed the International Civil Aviation Organisation and the International Telecommunication Union of its launch plans.
"Right now, we're carefully monitoring developments and are in close touch with the interested parties and the international organizations," Mr Haq said at UN headquarters in New York.