March 20 (UPI) -- North Korea has improved the performance of its rocket engine in the past six months, according to Seoul's defense ministry.
The development may be a sign Pyongyang has reached the final preparation stages of test launching an intercontinental ballistic missile.
The announcement comes a day after the test of a new high-thrust rocket engine was lauded as a "great leap forward" by North Korea on Sunday.
South Korea defense ministry spokesman Lee Jin-woo told reporters at a regular press briefing on Monday that Pyongyang has made "meaningful progress" in its weapons program in reference to the latest engine test, local news service EDaily reported.
But Lee also said "further analysis on the precise engine thrust and its future possible use is needed."
"The engine North Korea publicized -- and four auxiliary engines -- appear to be connected," Lee said. "We presume it is for developing a new engine."
On Sunday Pyongyang's Workers' Party newspaper Rodong Sinmun ran eight photographs of the high-thrust engine.
The images indicate the equipment is similar to a satellite rocket engine North Korea may have tested in September.
But the flames emitted from the rocket engine appeared to be stronger and more intense than the output from September's test. A secondary engine may also have been attached since September.
North Korea did not disclose information on rocket propulsion or burn time in its most recent announcement. It did however state its September 2016 rocket engine test emitted an 80-ton force thrust power that burned for 200 seconds.
North Korea may have improved engine thrust by boosting fuel efficiency and the performance of the combustion chamber, according to Seoul's defense ministry.
South Korea military officials who spoke anonymously to EDaily said it is now likely North Korea could test its missiles for atmospheric re-entry -- the last stage of ICBM development, according to the report.