North Korea conducted a “very important test” on Sunday at its Sohae satellite launch site, as nuclear negotiations between Pyongyang and Washington remain deadlocked.

A spokesman for the North’s National Academy of Science said,”A very important test was carried out at the Sohae Satellite Launch Site on December 7th, 2019″.

The North did not say what was tested on Saturday. But South Korea’s Joint Chiefs of Staff said that nothing has been fired from the North’s Sohae satellite launching station, also known as Donchang-ri site, Yonhap News Agency reported.

The North has reportedly shown signs of preparing for a missile engine test at the site recently, and Sunday’s claim could mean that it has successfully tested a new rocket engine that could be used in the launch of a new long-range rocket or an intercontinental ballistic missile (ICBM).

The test came as Pyongyang has ramped up pressure on the US to meet its demand for a new negotiating proposal by year’s end, strongly suggesting that otherwise, it could restart testing of nuclear weapons and ICBM.

On Saturday, South Korean President Moon Jae-in and his US counterpart Donald Trump agreed to maintain momentum for dialogue between Washington and Pyongyang, according to South Korea’s presidential office.

Last week, North Korea launched two “unidentified projectiles” on the Thanksgiving holiday in the US as nuclear talks between Pyongyang and Washington remain deadlocked.

Kim and US President Donald Trump adopted a vaguely-worded statement on the “complete denuclearisation of the Korean peninsula” at their first summit in Singapore in June last year, but little progress has since been made.

In August this year, North Korea fired two unidentified projectiles into the East Sea.

North Korea is under multiple sets of international sanctions over its nuclear weapon and ballistic missile programmes and lifting some of them was a key demand at the Hanoi summit.

North Korea repeatedly has issued warnings against the combined military exercise between South Korea and the US, threatening that it would seek “a new way” rather than engagement if Seoul goes ahead with such a rehearsal for invasion.