The US defence department has delayed an intercontinental ballistic missile test that had been planned for next week at an air force base in California amid mounting tensions with North Korea, according to a senior official.

Defence secretary Chuck Hagel reportedly decided to put off the long-planned Minuteman 3 test until next month because of concerns the launch could be misinterpreted and exacerbate the Korean crisis. "This is the logical, prudent and responsible course of action to take," the official said, speaking on condition of anonymity.

The test was not connected to the ongoing annual US and South Korean military exercises in that region that have angered North Korea.

The North's military warned this week that it was authorised to attack the US using "smaller, lighter and diversified" nuclear weapons. South Korean officials say North Korea has moved at least one missile with considerable range to its east coast – possibly the untested Musudan missile, believed to have a range of 1,800 miles (2,890km).

US officials have said the move suggests a North Korean launch could be imminent. But while Washington is taking the North Korean threats seriously, US leaders say they have seen no visible signs that the North is preparing for a large-scale attack.

North Korea held its latest nuclear test in February, and in December launched a long-range rocket that could potentially hit the continental US. Increasing tension is the uncertainty around the intentions of the country's new young leader, Kim Jong-un.

North Korea has been angered by increasing sanctions and the military exercises, which have included a broad show of force ranging from B-2 bombers and F-22 fighters to an array of warships. The exercises are scheduled to continue until the end of the month.

This week, the US said two of the navy missile-defence ships were moved closer to the Korean peninsula and that a land-based system is being deployed to the Pacific territory of Guam later this month.