Carney nevertheless said that the US would not be surprise if North Korea were to conduct a new missile test.
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"We would not be surprised to see them take such an action," Carney said. "We have seen them launch missiles in the past."
Over the past few years, North Korea has conducted some such tests after it was economically sanctioned by the west.
On Friday North Korea has warned diplomats in Pyongyang that it can't guarantee the safety of embassies in the event of a conflict and suggested they may want to evacuate their staff, Russia's top diplomat said.
North Korea's government did not comment on the embassy warnings. Tensions have been roiling in the past few weeks following a North Korean nuclear test and the country's subsequent warnings to South Korea and the United States that it would be prepared to attack.
"This is just an escalating series of rhetorical statements, and the question is, to what end?" US State Department spokeswoman Victoria Nuland told reporters in Washington.
"This is an unpredictable regime and an unpredictable situation," Nuland said.
"Our posture remains to be prudent, to take appropriate measures, in the defense and deterrence sphere, both for ourselves and for our allies, but to continue to urge the DPRK to change course, because this is not going to end their isolation."
The US Embassy in Seoul also issued a notice to Americans in South Korea, saying it had "no specific information to suggest an imminent threat to US citizens or facilities."
The UN says its staff was continuing to work in North Korea while Secretary-General Ban Ki-moon studied the North Korean message to consider evacuating UN personnel.
UN spokesman Martin Nesirky said a UN representative joined diplomats at a meeting Friday in Pyongyang and that UN staff "remain engaged in their humanitarian and developmental work throughout the country."
Asked whether Ban would go to Pyongyang, Nesirky said the UN chief has offered to facilitate dialogue "to help to bring people together."
"Dialogue is what's needed to try to turn the volume down. The volume has been turned up tremendously high in recent days and the volume needs to be turned back down again and the secretary-general is certainly keen to help," he said.
Nesirky added that the UN was "providing very important life-saving assistance to people, particularly children" in North Korea.
Reuters, AP contributed to this report
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