North Korea conducted another rocket engine test last Friday that could be used for an intercontinental ballistic missile, U.S. Defense Department officials told CNN on Monday.
It follows a widely publicized rocket engine test earlier this month that North Korean leader Kim Jong-un hailed as a "new birth" for the country's rocket industry.
"The officials said the latest engine trial is the third such test in recent weeks using similar technology," CNN added. It is unclear when the North conducted the second test.
To produce a deployable ICBM, the North needs the propellant technology to boost the engine thrust while preventing the warhead from being incinerated on re-entry into the Earth's atmosphere.
Since Kim took power, the regime has conducted a string of missile engine combustion tests to acquire the technology. The engine tested on March 18 allegedly had about 100 tons of thrust power.
Meanwhile, there is high chance of another missile launch or nuclear test by the North within 30 days, the Center for Strategic and International Studies in Washington said.