Politicians in Hawaii and Alaska are calling from improved defence against potential ballistic missile strikes after North Korea test-fired an intercontinental missile, which experts believe could hit the US.
Tuesday's launch saw North Korean leader Kim Jong-Un fire a new type of missile from Panghyon aircraft plant, a site not previously associated with his missile program, Pentagon spokesman Navy Captain Jeff Davis said.
Though the Pentagon initially said the missile was intermediate in range, updated analysis later showed its range "likely" exceeded 5,500 kilometres, making it capable of reaching Alaska and so changing its designation to intercontinental ballistic missile, Davis said.
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Fox News reports officials have called for action in Washington to defend the states closest to Pyongyang.
Senators Dan Sullivan of Alaska and Brian Schatz of Hawaii introduced legislation in May that would improve the capability and capacity of US homeland missile defence.
The bill would incorporate an additional 28 ground-based interceptors, 14, which would be located in Alaska.
On Tuesday, Senator Sullivan said the news of North Korea’s successful launch was “disturbing” for Alaskan residents.
“Now more than ever, it’s imperative for Alaskans and the rest of the nation that we be prepared,” he said.
The US has also warned it is ready to use force "if we must" but would prefer global diplomatic action.
The US ambassador to the United Nations, Nikki Haley, told a UN Security Council meeting that North Korea's actions were "quickly closing off the possibility of a diplomatic solution" and the US was prepared to defend itself and its allies.
"One of our capabilities lies with our considerable military forces. We will use them if we must but we prefer not to have to go in that direction," Haley said on Wednesday.
She urged China, North Korea's only major ally, to do more to rein in Pyongyang.
Haley said the US would propose new UN sanctions on North Korea in coming days and warned if Russia and China did not support the move then "we will go our own path".