Defense Secretary Chuck Hagel plans to unveil plans Friday to bolster US missile defenses to counter a growing threat from nuclear-armed North Korea, an administration official said Friday.
"This is a response to a threat from North Korea that has increased over time," the official, who spoke on condition of anonymity, told AFP.
Hagel was scheduled to make an announcement "on missile defense" at 3 pm local time (1900 GMT), the Pentagon said in a statement.
The US military already has 30 anti-missile interceptors on the Pacific coast, stationed at Fort Greely in Alaska and at Vandenberg air base in California.
A top Pentagon official, James Miller, undersecretary of defense for policy, said this week that the United States could quickly mobilize additional interceptors as a response to North Korea's provocations.
"North Korea's shrill public pronouncements underscore the need for the US to continue to take prudent steps to defeat any future North Korean ICBM (intercontinental ballistic missile)," Miller said at an event at the Atlantic Council think tank on Tuesday.
"We have the ability to swiftly deploy up to 14 additional Ground-Based Interceptors if needed," he added.
The Pentagon was also prepared to build a new missile field on the East Coast or to add more interceptors in Alaska "should either approach become necessary due to further future increases in the threat from Iran and North Korea," he said.
North Korea has missiles that can strike South Korea and Japan but has yet to demonstrate it has the capability to fire long-range missiles.
But US officials worry the North has made progress on that front, having put a satellite into orbit, while Pyongyang's nuclear weapons program underlines the potential threat.
North Korea has issued a wave of drastic threats in recent days and announced it has abandoned the 60-year-old armistice that ended the Korean War.