North Korea said it successfully performed another "crucial test" at its long-range rocket launch site that will further strengthen its nuclear deterrent.
The test - the second at the facility in a week, according to North Korea's Academy of Defense Science - possibly involved technologies to improve intercontinental ballistic missiles that could potentially reach the continental United States.
Pak Jong Chon, chief of the Korean People's Army's general staff, said on Saturday that North Korea has built up "tremendous power" and that the findings from the recent tests would be used to develop new weapons to allow the country to "definitely and reliably" counter US nuclear threats.
The North in recent weeks has been dialling up pressure to coax major concessions from the Trump administration as it approaches an end-of-year deadline set by leader Kim Jong Un to salvage faltering nuclear negotiations.
The 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 testing activity and defiant statements suggest that the North is preparing to do something to provoke the US if Washington doesn't back down and make concessions to ease sanctions and pressure on Pyongyang in deadlocked nuclear negotiations.
Kim, who unilaterally suspended nuclear and intercontinental ballistic missile tests last year during talks with Washington and Seoul, has said North Korea could seek a "new path" if the United States persists with sanctions and pressure against the North.
North Korea has also conducted 13 rounds of ballistic missile and rocket artillery tests since May, and has hinted at lifting its moratorium on nuclear and long-range missile tests if the Trump administration fails to make substantial concessions before the new year.
Some experts doubt that Kim would revive the tensions of 2017 by restarting nuclear and ICBM tests, which would cross a metaphorical "red line" and risk shattering his hard-won diplomacy with Washington.
They say Kim is likely to pressure Donald Trump with military activities that pose less of a direct threat to the US and by bolstering a united front with Beijing and Moscow. Both are the North's allies and have called for the UN Security Council to consider easing sanctions on Pyongyang to help nuclear negotiations move forward.