North Korea last conducted a nuclear test in September 2016. Pyongyang is getting its Punggye-ri nuclear test site ready for its next experiment, according to U.S. and South Korea officials. File Photo by Yonhap/UPI

March 24 (UPI) -- North Korea may be getting ready for its sixth nuclear test.

Intelligence collected from U.S. sources indicates North Korea's next test "could come as early as the end of the month," one official told Fox News.


There is evidence, according to the report, that North Korea has finished tunnels around the Punggye-ri nuclear test site.

But more equipment needs to be moved into the area for a test.

North Korea conducted two nuclear tests in 2016.

South Korea's military is generally in agreement with the U.S. assessment.

"When North Korea's top leadership makes the decision, we believe the country is ready to test nuclear weapons at any time," one official said, according to South Korean news service News 1.

The unidentified South Korean military official said the tunnels at the north and west sides of Punggye-ri have been completed, and a southern tunnel has also been drilled.

The U.S. military has begun to move the Air Force WC-135 Constant Phoenix to Japan for surveillance purposes.

The aircraft will be used to patrol areas surrounding the Korean peninsula.

If North Korea completes the miniaturization of nuclear warheads and mounts the weapon on an intercontinental ballistic missile, it will have a weapons capable of striking the U.S. mainland.

Seo Gyun-ryeol, a professor of nuclear engineering at Seoul National University, told News 1 that North Korea's fifth test may have resulted in a 6- to 10-kiloton explosion.

"This approximates the power of the atomic bomb dropped on Hiroshima," Seo said.