The South Korean military believes North Korea is likely to test-fire its new intermediate-range ballistic missile(IRBM) after claiming a successful test of a solid-fuel engine.

Joint Chiefs of Staff spokesperson Col. Lee Sung-joon said that the development of the IRBM is assessed to be the North's attempt to secure the capability to attack the UN Command's rear bases, including Guam, and the U.S. bases in Japan.

It is also likely meant to prevent an increase in U.S. forces and the UNC forces' support on the Korean Peninsula.

Calling the development a part of the North's first-phase activity to expand the development of a solid-fuel short-range ballistic missile(SRBM), IRBM and intercontinental ballistic missile(ICBM), the spokesperson said it poses a serious threat to world peace and stability.

He added that intelligence officials in South Korea and the U.S. continue to track down and monitor related technological developments, activities and provocations through close coordination.

On Wednesday, the North's state-run Korean Central News Agency reported that Pyongyang had successfully conducted ground expulsion tests for the first-phase and second-phase solid-fuel engines last Saturday and this Tuesday.