The US has successfully tested an interception system against intercontinental ballistic missiles, its military has announced.
The test, involving a simulated attack by an intercontinental ballistic missile, was announced by the US military, who not long after said it had been successful.
An interceptor was fired from Vandenberg Air Force Base in California, a Reuters witness at the base said.
"The intercept of a complex, threat-representative ICBM target is an incredible accomplishment ... a critical milestone for this program," Vice Admiral Jim Syring, the director of the Missile Defense Agency, said in a statement.
The test came as fears mount about North Korea's advancing program to develop an ICBM capability.
The country's leader Kim Jong-un has threatened the possibility of such an attack, with North Korea dramatically ramping up the pace of its missile tests over the past year with the goal of developing an ICBM that can strike the US mainland.
US Ambassador to the United Nations Nikki Haley said the country was negotiating with China when they should push for further United Nations Security Council action on North Korea, and could reach a decision this week.
UN diplomats, speaking on condition of anonymity, have said it appeared China was still only prepared to act if North Korea conducted a long-range missile launch or a nuclear test and that Beijing did not view the dozens of ballistic missile launches in the past year as warranting further UN sanctions.
The Security Council first imposed sanctions on Pyongyang in 2006 over its ballistic missile and nuclear programs and has ratcheted up the measures in response to five nuclear tests and two long-range missile launches. North Korea is threatening a sixth nuclear test.
US Secretary of State Rex Tillerson told the UN Security Council on April 28 the 15-member body needed to act before North Korea does. Just hours after the meeting, chaired by Mr Tillerson, Pyongyang launched yet another ballistic missile.
Within days the United States proposed to China that the Security Council strengthen sanctions on North Korea over its repeated launches. Traditionally, the US and China have negotiated new sanctions before involving the other 13 council members.
Since then, Pyongyang has launched several more ballistic missiles, including a short-range ballistic missile on Monday that landed in the sea off its east coast.
"Nothing is changing North Korea's actions," said Ms Haley.
She said it was time to say, "OK, what are we going to do if this is going to happen every other day?
"How should we respond in a way that we actually stop these things or slow it down?"
Haley said the United States believes "China is doing back-channel networking with North Korea in a way that's getting them to try and stop the nuclear testing. So we believe that they are being productive."