With Pyongyang launching test after provocative test to develop a miniaturized nuclear warhead and a missile capable of delivering that deadly payload to the United States, Obama's White House wants to ratchet up the pressure before he leaves office in January.
Contributing to the tensions as the United States undergoes a transfer of power to President-elect Donald Trump, is the possibility that North Korea will see it as a prime opportunity to test an inexperienced new US commander in chief.
"We don't view their progressive development of their capabilities as being anything other than a significant threat to our interests and that of our allies."
This pressure, she said, "has been building and will continue to build, certainly through the duration of this administration."
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A second US official said the issue would be high on the agenda when Obama and Xi meet on the margins of an Asia-Pacific summit in Lima, Peru.
North Korea has conducted two nuclear tests this year and test-fired a series of missiles.
Sanctions are already in the works at the United Nations to target North Korea's coal exports to China, diplomats said -- a vital source of revenue for the regime.
Pyongyang has used loopholes in previous sanctions to increase coal exports by as much as 60 percent, netting more than 100 million dollars a month in much needed income.