North Korea said Saturday it successfully performed another “crucial test” at its long-range rocket launch site that would further strengthen its nuclear deterrent.

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 was conducted 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.