The United States is prepared to shoot down a North Korean missile launch or test "if it were coming towards our territory or the territory of our friends and allies," Carter said during an appearance on NBC's "Meet the Press."
North Korea declared on Sunday it can test-launch an intercontinental ballistic missile at any time from any location set by leader Kim Jong Un, saying a hostile U.S. policy is to blame for its arms development.
Kim said on Jan. 1 that his nuclear-capable country was close to test-launching an intercontinental ballistic missile (ICBM).
"The ICBM will be launched anytime and anywhere determined by the supreme headquarters of the DPRK," an unnamed Foreign Ministry spokesman was quoted as saying by the official KCNA news agency, using the acronym for the country's name.
The North is formally known as the Democratic People's Republic of Korea.
The United States said on Jan. 5 that North Korea had demonstrated a "qualitative" improvement in its nuclear and missile capabilities after an unprecedented level of tests last year.
North Korea has been testing rocket engines and heat-shields for an ICBM while developing the technology to guide a missile after re-entry into the atmosphere following a lift-off, experts have said.
While Pyongyang is close to a test, it is likely to take some years to perfect the weapon, according to the experts.
Once fully developed, a North Korean ICBM could threaten the continental United States, which is around 9,000 km (5,500 miles) from the North. ICBMs have a minimum range of about 5,500 km (3,400 miles), but some are designed to travel 10,000 km (6,200 miles) or further.
U.S. President-elect Donald Trump responded to Kim's comments on an ICBM test by declaring in a tweet last week that "It won't happen!"
A U.S. State Department spokesman said last week that the United States does not believe that North Korea is capable of mounting a nuclear warhead on a ballistic missile.
North Korea has been under U.N. sanctions since 2006 over its nuclear and ballistic missile tests. The sanctions were tightened last month after Pyongyang conducted its fifth and largest nuclear test on Sept. 9.
"The U.S. is wholly to blame for pushing the DPRK to have developed ICBM as it has desperately resorted to anachronistic policy hostile toward the DPRK for decades to encroach upon its sovereignty and vital rights," KCNA quoted the spokesman as saying.
"Anyone who wants to deal with the DPRK would be well advised to secure a new way of thinking after having clear understanding of it," the spokesman said, according to KCNA.