Washington, Seoul and Tokyo have condemned Pyongyang’s decision to launch a long-range rocket this month, after North Korea notified UN agencies of the plan.

Reports emerged on Tuesday that North Korea had told the International Maritime Organization it would launch a satellite between February 8 and 25, as well as sending a report to the International Telecommunication Union that was less specific on timing. Governments are obliged to provide such warnings to minimise the risk to international air and sea traffic.

The news comes as the UN Security Council considers how to respond to Pyongyang’s fourth nuclear test last month. It condemned two previous satellite launches in 2012 as a breach of resolutions imposed following Pyongyang’s first nuclear test in 2006, which block it from “any launch that uses ballistic missile technology, even if characterised as a satellite launch”.

A successful launch would heighten concerns in Washington that North Korea may soon be able to target the US mainland with a nuclear strike. Senior US officials believe Pyongyang is already able to create warheads small enough to be used with an intercontinental missile, and analysts think last month’s test may have employed a “boosted” device more powerful than those previously tested.

“We’re not asking for some sort of pre-emptive resolution here to a launch that hasn’t occurred,” said a US State Department spokesman, referring to US efforts to secure Chinese support for more powerful sanctions against North Korea. “But the announcement of it itself is just all the more indication that the international community needs to get behind tougher action against them.”

Shinzo Abe, Japan’s Prime Minister, said he would work with other nations to “strongly demand” that North Korea call off the launch, while Cho Tae-yong, a national security adviser to South Korean President Park Geun-hye, warned that Pyongyang would pay a “severe price” if it went ahead with its plan.

Last week satellite photography analysis published on the 38 North website run by Johns Hopkins University of the US noted apparent preparations for a launch at North Korea’s Sohae rocket site.

Separate image analysis of the Yongbyon nuclear site, published on Monday by the Institute for Science and International Security, suggested possible construction of “an isotope separation facility, including tritium separation”.

Tritium is a radioactive hydrogen isotope that can be used to boost fission-based nuclear bombs, or in much more powerful thermonuclear weapons. Pyongyang claims its latest test was of the latter breed of device but this has drawn widespread scepticism abroad.