North Korea conducted three rocket engine tests in March.
For instance, the USA side completely stop military exercises, temporarily or permanently.
United States officials speaking anonymously to several news agencies said the latest engine test, on Thursday, could be one stage of an intercontinental ballistic missile (ICBM) engine that would be able to reach the US.
Recent reports suggest that North Korean restaurants in Southeast Asian countries-such as Cambodia, Vietnam, and Thailand-are also experiencing a decline in business.
"I made today's visit because I recognized the need to assure the South Korean people that our military has a strong missile capability", said Moon after watching the test, "People will now be proud of our military as they know our missile capability does not lag behind North Korea's".
South Korea has tested the missile four times so far and will have it ready to use after two additional tests, Mr. Moon's office said.
The United States has tried for years to discourage South Korea from developing longer-range ballistic missiles in keeping with the Missile Technology Control Regime, a voluntary worldwide arms-control pact.
However, the Chinese Foreign Ministry spokesman questioned such calls.
The US has also urged China, Pyongyang's sole ally, to exert more economic and diplomatic pressure on North Korea to help rein in its nuclear and missile programmes.
Do claimed he intends to discuss possible ways to ensure North Korea's participation at Pyeongchang 2018 with the IOC.
"If a North Korean delegation takes part in the Pyeongchang Winter Olympics, I believe it will greatly contribute to realizing the Olympic values, which are about bringing humanity together and promoting world peace", he further said, according to a script of his comments released by the presidential Blue House. While that has been a non-starter for the U.S., experts say this could be an opening gambit from Pyongyang.
He added that the worldwide community is infuriated by the death of American Otto Warmbier who died six days after North Korea freed him on June 13. The editorial alleged Trump is considering launching a preemptive strike against North Korea to divert attention from domestic political problems.
United States officials, speaking anonymously to news agencies, said the engine could potentially be fitted to an intercontinental ballistic missile (ICBM).
The U.S.is concerned about the rapid progress of Pyongyang's nuclear and missile program due to fears that the country could soon acquire the capability to hit the U.S. with nuclear capable missiles.