The toughly worded US statement called on "all states" to show the North that any unlawful actions would have "consequences."
It was issued by the Pentagon at a sensitive time -- just weeks before President Barack Obama is due to hand power over to his successor, Donald Trump.
The statement came hours after Kim Jong-un, the North Korean leader, said his country was close to testing such a missile, which would be capable of reaching American shores.
"We are in the final stages of test-launching the intercontinental ballistic missile," Kim said in a televised New Year's speech, pointing to a string of nuclear and missile tests last year.
He said Pyongyang was now a "military power of the East that cannot be touched by even the strongest enemy."
The Pentagon statement noted that "multiple UN Security Council resolutions explicitly prohibit North Korea's launches using ballistic missile technology."
It urged Pyongyang to "refrain from provocative actions and inflammatory rhetoric that threaten international peace and stability."
The statement reaffirmed Washington's "ironclad commitment" to defend its allies, using "the full spectrum of US extended deterrence capabilities."
Pyongyang has never successfully test-fired an intercontinental ballistic missile (ICBM), and analysts are divided over how close it is to doing so.
But all agree it has made enormous strides in that direction since Kim took over as leader from his father Kim Jong-Il, who died in December 2011.
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Trump requested North Korean briefing
According to a senior US intelligence official, President-elect Donald Trump's first, and at that time only, request for a special classified intelligence briefing was for one on North Korea and its nuclear weapons programme.
North Korea and its nuclear programme has also been of interest to retired Lieutenant General Michael Flynn, Trump's choice for national security advisor and a former director of the Defense Intelligence Agency.
An Chan-il, a former North Korean military officer who defected to the South and runs a think tank in Seoul, said Kim will gauge Trump's comments about his country for potential interest in dialogue and determine whether to try and conduct an ICBM test launch.
"If Trump comes in and the North does not get a good signal in terms of how the relationship between the two countries is going to go, that’ll give them another reason to do it," An said.
Kim also said that the North would continue to develop its pre-emptive nuclear strike capability if the United States and South Korea continue to conduct annual joint military exercises.
There are 28,500 U.S. troops based in South Korea, and North Korean state media often describes annual joint exercises as preparation for an attack.
In February, North Korea launched a satellite into space, which was widely seen as a test of long-range ballistic missile technology.
A senior U.S. military official said last month that North Korea appears able to mount a miniaturised nuclear warhead on a missile but is still struggling with missile re-entry technology necessary for longer range strikes.
Although it fired a variety of missile types last year, North Korea is not known to have test-launched a ballistic missile since October.
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