China is seen as North Korea's main ally and the USA hopes Beijing can have greater influence on the state to stop both its missile tests and nuclear program.
South Korea began developing Hyunmoo-2 after a 2012 agreement with its ally, the United States, to increase the range of its weapons to 500 miles and raise the warhead limit to 1,100 pounds. The North has carried out two atomic tests and dozens of missile launches since the beginning of past year in its quest to develop a missile capable of delivering a nuclear warhead to the continental United States - something Trump has vowed "won't happen".
The officials told Fox News that the latest engine test on Thursday was conducted in the city of Yun Song, where previous rocket tests have taken place.
South Korean officials did not have details about the reported test and declined to comment on the possible nature of the engine.
The United States, South Korea and others often accuse North Korea of using foreign detainees to wrest diplomatic concessions.
We've learned North Korea might also be willing to at least temporarily suspend its missile and nuclear tests.
"We've said many times that China is making unremitting efforts to resolve the Korean peninsula nuclear issue, and plays an active and constructive role", he said.More news: Northam leads Gillespie in Virginia governor's race, poll finds
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"I think that the weapon systems that the Agency for Defense Development is working on are means not of destruction and slaughter but rather of dialogue and peace", Moon was also quoted as saying by Park.
However, experts say Pyongyang could still be years away from have a reliable ICBM capability.
His family and others have blamed North Korea for his condition. ICBMs have a minimum range of about 3,400 miles (5,500 km), but some are created to travel 6,200 miles (10,000 km) or farther.
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.
"Judging from the speed of North Korea's advancements in nuclear and missile technologies I believe they will acquire such capability in the near future".
Park didn't say how far the Hyunmoo-2 missile flew or where it landed, but said it accurately hit its target area.