WASHINGTON (AFP) - The Pentagon has delayed an intercontinental ballistic missile test due to take place in California next week amid soaring nuclear tensions with North Korea, an official said on Saturday.

The defence official told AFP that Defence Secretary Chuck Hagel rescheduled the Minuteman 3 test at Vandenberg Air Force Base for some time next month due to concerns the launch "might be misconstrued by some as suggesting that we were intending to exacerbate the current crisis with North Korea."

"We wanted to avoid that misperception or manipulation," the US official added.

"We are committed to testing our ICBMs to ensure a safe, secure, effective nuclear arsenal." North Korea, incensed by UN sanctions and South Korea-US military drills, has issued a series of apocalyptic threats of nuclear war in recent weeks.

The Pentagon's announcement followed reports that the North had loaded two intermediate-range missiles on mobile launchers and hidden them in underground facilities near its east coast.

They were reported to be untested Musudan missiles which are believed to have a range of around 3,000km that could theoretically be pushed to 3,999km with a light payload.

That would cover any target in South Korea and Japan, and possibly even reach US military bases located on the Pacific island of Guam.

The North has no proven inter-continental ballistic missile capability that would enable it to strike more distant US targets, and many experts say it is unlikely it can even mount a nuclear warhead on a mid-range missile.

Nevertheless, the international community is becoming increasingly skittish that, with tensions showing no sign of de-escalating, there is a real risk of the situation spiraling out of control.

The latest crisis erupted when North Korea fired a long-range rocket in December that could theoretically reach the continental United States, but instead splashed down near the Philippines.

The North later carried out its third nuclear test in February, defying even its main ally China.

The UN Security Council on March 7 unanimously approved new sanctions that include greater scrutiny of shady financial dealings by the impoverished regime.