SEOUL/WASHINGTON (Reuters) – North Korea told U.N. agencies on Tuesday it plans to launch a satellite as early as next week, a move that could advance the country’s long-range missile technology after its fourth nuclear test on Jan. 6.

News of the planned launch between Feb. 8 and Feb. 25 drew fresh U.S. calls for tougher U.N. sanctions already under discussion in response to North Korea’s nuclear test. State Department spokesman John Kirby said the United Nations needed to “send the North Koreans a swift, firm message.”

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

“We have received information from DPRK regarding the launch of earth observation satellite ‘Kwangmyongsong’ between 8-25 February,” a spokeswoman for the International Maritime Organization, a U.N. agency, told Reuters by email.

The International Telecommunication Union, another U.N. agency, told Reuters 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.

It said the information provided by North Korea, whose official name is the Democratic People’s Republic of Korea, was incomplete, and that it was seeking more details.

U.S. officials said last week that 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.

The White House said on Tuesday that any satellite launch by North Korea would be viewed as “another destabilizing provocation.” U.S. Assistant Secretary of State Daniel Russel, the senior U.S. diplomat for East Asia, told reporters it “argues even more strongly” for tougher U.N. sanctions.

Russel said a launch, “using ballistic missile technology,” would be an “egregious violation” of North Korea’s international obligations.

He said it showed the need “to raise the cost to the leaders through the imposition of tough additional sanctions and of course by ensuring the thorough and rigorous enforcement of the existing sanctions.”

Russel said negotiations were “active” at the United Nations and that the United States and North Korea’s main ally China “share the view that there needs to be consequences to North Korea for its defiance and for its threatening behaviors.”

“Our diplomats are in deep discussion in New York about how to tighten sanctions, how to respond to violations,” he said.

Asked about China’s cautious response to U.S. calls for stronger and more effective sanctions on Pyongyang and Beijing’s stress on the need for dialogue, Russel said:

“Yet another violation by the DPRK of the U.N. Security Council resolution, coming on the heels of its nuclear test, would be an unmistakable slap in the face to those who argue that you just need to show patience and dialogue with the North Koreans, but not sanctions.”

White House spokesman Josh Earnest said China had “unique influence over the North Korean regime” and added: “we … certainly are pleased to be able to work cooperatively and effectively with the Chinese to counter this threat.”

Earlier on Tuesday, China’s envoy for the North Korean nuclear issue arrived in the capital Pyongyang, the North’s KCNA news agency reported.

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

Western and Asian experts have said that launch was part of an effort to build an intercontinental ballistic missile.

North Korea has shown off two versions of a ballistic missile resembling a type that could reach the U.S. West Coast, but there is no evidence the missiles have been tested.

Pyongyang is also seen to be working to miniaturize a nuclear warhead to mount on a missile, but many experts say it is some time away from perfecting such technology.

North Korea said it successfully tested a hydrogen bomb last month but this was met with skepticism 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 Jack Kim in Seoul, Nobuhiro Kubo in Tokyo and David Brunnstrom, Ayesha Rascoe, Mohammad Zargham and Doina Chiacu in Washington; Editing by Mark Heinrich and Grant McCool)