One day after Rex Tillerson warned that the US is contemplating a pre-emptive military attack on North Korea, the isolated nation announced it has conducted a ground test of a new type of high-thrust rocket engine that leader Kim Jong Un is calling a “revolutionary breakthrough” for the country’s space program, the North’s state media said Sunday. Kim attended Saturday’s test at the Sohae launch site, according to the Korean Central News Agency, which said the test was intended to confirm the “new type” of engine’s thrust power and gauge the reliability of its control system and structural safety.

A previous demonstration of a “new rocket engine” in this undated photo released
by North Korea’s KCNA in Pyongyang September 20, 2016

Kim called the test “a great event of historic significance” for the country’s indigenous rocket industry, the KCNA report said. He also said the “whole world will soon witness what eventful significance the great victory won today carries” and claimed the test marks what will be known as the “March 18 revolution” in the development of the country’s rocket industry. The report indicated that the engine is to be used for North Korea’s space and satellite-launching program.

The claim of a successful test of the high-thrust rocket engine would put North Korea a step closer to being able to launch an intercontinental ballistic missile, as Mr. Kim said the country would do this year in his new-year address, the WSJ reported.

North Korea is banned by the United Nations from conducting long-range missile tests, but it claims its satellite program is for peaceful use, a claim many in the U.S. and elsewhere believe is questionable.

As AP further reports, North Korean officials have said that under a five-year plan, they intend to launch more Earth observation satellites and what would be the country’s first geostationary communications satellite — which would be a major technological advance. Getting that kind of satellite into place would likely require a more powerful engine than its previous ones. The North also claims it is trying to build a viable space program that would include a moon launch within the next 10 years.

Saturday’s engine test, at North Korea’s Sohae Satellite Launching Station, near its border with China, came as U.S. Secretary of State Rex Tillerson was en route to Beijing for a series of meetings with Chinese leadership that were to include discussions about how to rein in Pyongyang’s nuclear threat. On Friday, Tillerson told reporters in Seoul that the U.S. wasn’t interested in conducting direct talks with North Korea to halt its weapons program, saying instead that tighter sanctions enforcement and the possibility of a military strike were being considered as part of a continuing North Korea policy review by the White House.

“All options are on the table,” Tillerson said.

It’s unclear whether this test was deliberately timed to coincide with Tillerson’s visit, but Pyongyang has been highly critical of ongoing U.S.-South Korea wargames just south of the Demilitarized Zone and often conducts some sort of high-profile operation of its own in protest. Earlier this month, it fired off four ballistic missiles into the Sea of Japan, reportedly reaching within 200 kilometers (120 miles) of Japan’s shoreline.

Japan, which was Tillerson’s first stop before traveling to South Korea and China, recently held its first civilian missile evacuation drill over concerns of an unexpected North Korean attack.

While building ever better long-range missiles and smaller nuclear warheads to pair with them, North Korea has marked a number of successes in its space program. It launched its latest satellite — the Kwangmyongsong 4, or Brilliant Star 4 — into orbit on Feb. 7 last year, just one month after conducting what it claims was its first hydrogen-bomb test. It put its first satellite in orbit in 2012, a feat few other countries have achieved. In 2013, rival South Korea launched a satellite into space from its own soil for the first time, though it needed Russian help to build the rocket’s first stage.

In a controversial attempt to contain the threat from a potential North Korean missile attack, last week, the US military also began the deployment of its THAAD anti-missile system in S. Korea, despite Russia and China objecting to the move as being “counter-productive.” Beijing said THAAD’s deployment was harming the “regional strategic balance,” since it might damage China’s nuclear deterrent capabilities and potentially fuel US first-strike ideas. Moscow said Washington was “instigating an arms race in the subregion.”

“We do not oppose South Korean taking necessary measures to protect its security, but these measures cannot be based upon harming the security interests of South Korea’s friendly neighbor, China,” Chinese Foreign Ministry spokeswoman Hua Chunying said on Friday, as quoted by Reuters. Washington and Seoul however continue to maintain that the deployment of THAAD is a “defensive” measure against Pyongyang, and countries “other than North Korea” have nothing to worry about, according to US Defense Secretary James Mattis