The test possibly involved technologies to improve intercontinental ballistic missiles that could potentially reach the continental United States.

The announcement comes as North Korea continues to pressure the Trump administration for major concessions as it approaches an end-of-year deadline set by leader Kim Jong Un to salvage faltering nuclear negotiations.

North Korea’s Academy of Defense Science did not specify what was tested on Friday. Just days earlier, the North said it conducted a “very important test” at the site on the country’s northwestern coast, prompting speculation that it involved a new engine for either an ICBM or a space launch vehicle.

The announcement suggests that the country is preparing to do something to provoke the United States if Washington doesn’t back down and make concessions to ease sanctions and pressure on Pyongyang in deadlocked nuclear negotiations.

An unnamed spokesman for the academy said scientists received warm congratulations from members from the ruling Workers’ Party of Korea Central Committee who attended the test that lasted from 10:41 to 10:48 p.m. Friday at the Sohae Satellite Launching Ground, where the North has conducted satellite launches and liquid-fuel missile engine tests in recent years.

The spokesman said the successful outcome of the latest test, in addition to the one on Dec. 7, “will be applied to further bolster up the reliable strategic nuclear deterrent of the Democratic People’s Republic of Korea,” referring to North Korea’s formal name.

Kim Dong-yub, a former South Korean military officer and currently an analyst from Seoul’s Institute for Far Eastern Studies, said the North mentioning its nuclear deterrent makes it clear it tested a new engine for an ICBM, not a satellite-launch vehicle. Kim said it was notable that North Korea announced the specific length of the test, which he said possibly signals a larger liquid-fuel ICBM engine.

North Korea’s current ICBMs, including the Hwasong-15, are built with first stages that are powered by a pair of engines that experts say are modelled after Russian designs. When the North first tested the engine in 2016, it said the test lasted for 200 seconds and demonstrated a thrust of 80 tons-force.

Donald Trump touched down South Korea Saturday following the G-20 summit in Osaka, Japan and said he will visit the heavily-fortified demilitarized zone that separates North and South Korea.

But before that, Donald Trump was treated with some K-pop diplomacy. After meeting with President Moon Jae-in at the Blue House, he was greeted by EXO, a pop group whose members gave the president a book.

Turning a lot of eyebrows, the group also gave a signed copy of their album to White House adviser Ivanka Trump and chatted with the president’s son in law Jared Kushner.

This wasn’t the first time that Donald Trump’s daughter met the group. Harry Harris, United States ambassador to South Korea, shared a group picture from Saturday, adding that the first time she met the group was during the PyeongChang 2018 Olympic Winter Games.

Donald Trump floated the likelihood of meeting North Korean leader Kim Jong Un during his visit to the DMZ, a trip he unexpectedly announced on Friday.

“After some very important meetings, including my meeting with President Xi of China, I will be leaving Japan for South Korea (with President Moon). While there, if Chairman Kim of North Korea sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!” he wrote in a tweet.

During a press conference in Japan earlier today, Donald Trump said that he would be “very comfortable” to cross into North Korea after the meeting with Kim, a move which would make him the first United States president to cross the border while he’s at the DMZ.

He said his offer to meet Kim was a “feeler” and was a spontaneous plan who recently came up with.

“I just put out a feeler, because I don’t know where he is right now, he may not be in North Korea,” Trump told reporters.

“We may be meeting with Chairman Kim. We get along. There’ve been no nuclear tests, no long-range nuclear tests and they returned our hostages,” he added.