WASHINGTON - Experts say North Korea appeared to have conducted a fuel engine test on the ground, potentially for a long-range missile, in what Pyongyang claimed as "the test of great significance."
Michael Elleman, director of the Non-Proliferation and Nuclear Policy Program at the International Institute for Strategic Studies (IISS), said it is safe to assume North Korea conducted "a static engine test" but cannot conclude the type of engine tested based on currently available information.
A static engine test means the engine was tested on the ground with a missile component but without launching an actual missile into the air.
"The size of the engine, whether it was based on liquid or solid fuel, or the success of the test are impossible to know without more evidence, photographs," said Elleman. He added that it is also difficult to determine if the engine tested was "a new type or a test of an existing model."
North Korea said "a very important test took place at the Sohae Satellite Launching Ground" on Saturday afternoon, according to a statement issued on Sunday by the country's official Korean Central News Agency (KCNA).
"The results of the recent important test will have an important effect on changing the strategic position of the DPRK once again in the near future," said a spokesperson for the Academy of the National Defense Science of North Korea. The DPRK stands for Democratic People's Republic of Korea, North Korea's official English name.
Pyongyang did not give further details about the weapon it tested.
Choi Hyun-soo, a spokesperson for South Korean Defense Ministry, on Monday said, "We are aware of North Korea's announcement" without making a public assessment of the test.
The spokesperson said Seoul is continuing to work closely with Washington to monitor activities around major test sites in North Korea including Dongchang-ri, the site of the Sohae facility.
Bruce Bechtol, a former intelligence officer at the U.S. Defense Intelligence Agency and now a professor of political science at Angelo State University in Texas, said it is difficult to determine what kind of engine North Korea tested because it broke with recent practice and did not release any photos of the test.
Bechtol said the U.S. and South Korea governments may have images of the test. However, they have remained silent on the kind of weapons North Korea tested, he added.
Ian Williams, deputy director of the Missile Defense Project at the Center for Strategic and International Studies (CSIS), expressed concern that the type of engine North Korea tested is "a larger solid fuel rocket engine" for a long-range missile.
He said the next technology North Korea is probably looking to test is a long-range missile using a solid fuel engine because it had already tested a liquid fuel engine for an inter-continental ballistic missile (ICBM). He said all the short-range missiles North Korea tested this year are propelled by solid fuel engines.
"A big advance to them would be if they could get their longer-range missiles, move them into the use of solid fuel, which makes them much more operationally useful," said Williams.
Missiles using solid fuel engines are harder to detect because it takes shorter time to prepare than missiles using liquid fuel engines. Two years ago, physicist David Wright wrote that North Korea's ICBMs are capable of reaching the continental U.S.
Bruce Bennett, a senior defense analyst at the Rand Corporation, said although it is hard to determine what kind of rocket engine North Korea tested and whether the engine is for solid or liquid fuel, "the test stand that was used [to place an engine for the test] was apparently designed for testing ICBM engines."
Bennett said, however, the test "does not prove that the North Koreans are building their own ICBM engines, but they certainly want to imply that is the case."
He added, "If the engine [North Korea] tested this weekend really was of an ICBM engine, and the test succeeded, then North Korea would pose a more serious threat to the United States in the future. And that would change the North Korean strategic position."
Days ahead of the test, activities were detected at Sohae Satellite Launching Station, according to satellite imagery captured by Planet Lab on Thursday, which was reported by CNN.
North Korea has reportedly rebuilt the launch site after dismantling it partially when denuclearization talks with the U.S. began last year.
The talks remain stalled without much progress made since the Singapore Summit held in June 2018 due to their differences. Washington has been demanding Pyongyang take full denuclearization while Pyongyang wants Washington to relax sanctions first. The two have remained locked in their position since the Hanoi Summit held in February.
The most recent test came as North Korean ambassador to the United Nations said on Saturday that denuclearization is off the table in talks that he described as a "time-saving trick" to benefit a "domestic political agenda" of the U.S.
Prospects for any talks with North Korea seem to be diminishing further as Pyongyang returned belittling U.S. President Donald Trump on Monday.
Calling Trump "a heedless and erratic old man," former North Korean nuclear negotiator Kim Yong-chol said, "We have nothing more to lose." He continued, "The time when we cannot but call him a 'dotard' again may come" through a statement released by the KCNA.
Pyongyang called Trump a "dotard" when it exchanged threats and insults with Washington in 2017 while testing missiles. Trump resorted to calling Kim a "rocket man," an expression he used in reference to Kim in 2017.
In a separate statement issued by the KCNA on Monday, Ri Su-yong, vice-chairman of the Central Committee of North Korea ruling Workers' Party, said, "Trump might be in great jitter, but he had better accept the status quo that as he sowed, so he should reap, and think twice if he does not want to see bigger catastrophic consequences."
Pyongyang's two statements follow Trump's Sunday Twitter message. Trump said Kim "has far too much to lose, everything actually, if he acts in a hostile way" in response to North Korea's test.
Trump warned Kim not to jeopardize the "special relationship" with him or "interfere with the U.S. Presidential Election in November.
On Monday, a State Department official said the U.S. plans to ask the United Nations Security Council to discuss North Korean provocations including the test on Saturday during its meeting this week.