The U.S. administration of President Joe Biden plans to keep its North Korea policy flexible, while building on a 2018 summit agreement that included Pyongyang's commitment toward denuclearization, according to a senior official.

The Biden administration wants "maximum flexibility" in the process of dealing with Pyongyang, the official said as he explained why the diplomatic strategy on the issue is unlikely to be detailed in public.

North Korean leader Kim Jong Un is pictured at the congress of the Workers' Party in Pyongyang. (KCNA/Kyodo)

The remarks were made during a conference call to preview the meeting between Biden and South Korean President Moon Jae In in Washington on Friday, during which the North Korean nuclear issue is expected to be high on the agenda.

The Biden administration said in late April that it has finished its months-long policy review on North Korea, which calls for "a calibrated, practical" diplomacy toward the goal of "a complete denuclearization of the Korean Peninsula."

The details have remained unclear, other than that the plan is to seek a middle ground between the approaches taken by Biden's two most recent predecessors, Donald Trump and Barack Obama.

Trump, who in 2018 became the first sitting U.S. leader to meet North Korean leader Kim Jong Un, had pushed for a "big deal" under which all sanctions would be lifted if North Korea gave up all of its nuclear and other weapons of mass destruction.

Under the Obama administration, in which Biden served as vice president for eight years through January 2017, Washington adopted a "strategic patience" policy, designed to put more pressure on the reclusive country while waiting for it to return to denuclearization talks.

Both administrations failed to make substantial progress in ridding Pyongyang of its nuclear arsenal.

The senior official acknowledged during the conference call that the Biden administration will still inherit the agreement reached between Trump and Kim during their first summit in Singapore in 2018 as well as other agreements made by previous administrations.

In a joint statement following the Singapore summit, Trump and Kim said Washington would provide security guarantees to Pyongyang in return for a "complete" denuclearization of the peninsula.

A security guarantee is seen as a key incentive for North Korea to give up its nuclear arms. The United States and North Korea are still technically in a state of war as the 1950-1953 Korean War ended in a cease-fire rather than a peace treaty.

Asked about the possibility of coming up with an end of war declaration in its communications with North Korea, the Biden administration official said, "At this juncture, it's really not in our interest to preview or comment on specific issues like an end of war declaration in hopes of spurring dialogue."

But he noted that "a significant amount" of Moon's visit will be spent discussing the challenges posed by North Korea and how Washington and Seoul can move forward together in "dialogue and deterrence."

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