The Democratic People's Republic of Korea (North Korea) has reportedly tested an engine designed for an intercontinental ballistic missile (ICBM).
The engine's ground test is said to have been conducted at the country's long-range missile launch site near the west coast.
The new engine has been designed to facilitate the South Asian nation with the ability to launch a nuclear strike, North's official Korean Central News Agency reported.
A statement by US State Department spokesman Mark Toner was cited by AFP that urged North Korea to "refrain from actions and rhetoric that further destabilise the region and focus instead on taking concrete steps toward fulfilling its commitments and international obligations."
North Korea did not disclose the name of the tested ICBM. However, analysts viewed it as a KN-14, an upgraded version of the KN-08, reported Korea Times.
South Korean defence specialist Yang Uk was quoted by Yonhap as saying: "North Korea appears to be seeking to prove its missile capability in technical stages, as it's difficult to show the actual launch of an ICBM.
"The North is apparently asserting that it is capable of attacking the US mainland any time it wants."
Last week, North Korea launched a ballistic missile near the east coast peninsula amidst the two-day Nuclear Security Summit that was hosted by US President Barack Obama in Washington.
Meanwhile, US Defense Secretary Ashton Carter said that a proposed deployment of a US missile system in South Korea "is going to happen".