President Joe Biden's nominee for secretary of state, Antony Blinken, said on Tuesday the new administration planned a full review of the US approach to North Korea to look at ways to increase pressure on it to return to the negotiating table.
White House spokeswoman Jen Psaki reiterated this on Friday, saying North Korea's nuclear weapons were a serious threat to peace and Washington had a vital interest in deterring Pyongyang.
Sydney Seiler, the US national intelligence officer for North Korea, told the Center for Strategic and International Studies think tank earlier that Pyongyang's weapons development had been a consistent policy for 30 years.
"Every engagement in diplomacy has been designed to further the nuclear program, not to find a way out... I just urge people not to let the tactical ambiguity obstruct the strategic clarity about North Korea that we have," he said.
"So we should not be overly encouraged if suddenly (North Korea leader Kim Jong Un) proposes dialog tomorrow, nor should we be overly surprised, or discouraged, if there's an ICBM (intercontinental ballistic missile) launch by Sunday."
Seiler also said humanitarian aid - which Blinken said the United States should look at providing to North Korea if needed - was not something of interest to Pyongyang.
The force North Korea seeks to develop, while part aspirational and part years away, was far more than that needed by a country that simply wanted to be left alone, Seiler said, adding: "That is where the real risk of inaction comes in."
On Tuesday, Blinken had spoken of the review plan in response to a question by Democratic Senator Ed Markey, who asked whether Blinken would, with the ultimate aim of North Korea denuclearizing, support a "phased agreement" that offered tailored sanctions relief to Pyongyang in return for a freeze in its weapons programs.
Biden's top Asia official, Kurt Campbell, has said the administration must decide its approach quickly and not repeat an Obama-era delay that led to "provocative" steps by Pyongyang that prevented engagement.Campbell also had some praise for former President Donald Trump's unprecedented summits with Kim, although these made no progress in curtailing a North Korean nuclear weapons program that expanded in the meantime.