This technology can later use to create an Intercontinental missile capable of reaching the US West coast.
North Korea has tested a new rocket engine as part of its efforts to build a missile capable of reaching the American mainland, United States officials said.
The US official confirmed to AFP that Pyongyang tested a rocket engine on Thursday, on condition of anonymity and without providing further details.
It can be used to build Intercontinental ballistic missiles.
US officials have warned that North Korea is on the path to successfully developing an ICMB capable of hitting the United States unless something changes.
News of the recent test in the North came a day after Tillerson urged China, Pyongyang's sole ally, to put more pressure on the North to rein in its atomic weapons and ballistic missile programmes.
The disclosure of the engine test came a day after the U.S. pressed China to exert more economic and diplomatic pressure on North Korea to help rein in its nuclear and missile programmes, during a round of high-level talks in Washington.
Can You Spot the New features of the Blackhawks' 2017-18 Jersey?
BUFFALO, NY- The Sabres released pictures on Twitter Tuesday night of the changes they made to their uniforms. Along with any design changes, Adidas also boasts that the new jerseys are lighter , cooler and stronger.
The officials said it is not yet clear if the activity indicates a sixth nuclear test is imminent, but noted there is concern that North Korea could set off a test during Wednesday's visit to Washington by top Chinese diplomats and military officials.
The US has also ramped up its military presence in the region, conducting drills with Japan as well as South Korea, and is installing a controversial missile defence system in Seoul, known as Terminal High-Altitude Area Defence system (Thaad).
On March 18th, North Korean media reported that leader Kim Jong-un observed a successful testing of a homegrown ICBM engine.
Any military solution to the North Korea crisis would be "tragic on an unbelievable scale", Trump's defense secretary, Jim Mattis, said last month.
North Korea however did not publicise details of the test; it is usually quick to do so with successful ones.
In March after North Korea conducted three rocket engine tests.