President Donald Trump's abrupt decision to cancel his meeting with Kim Jong Un was a cumulative response to several belligerent North Korean diatribes during the past two weeks.

Most notably, First Vice Foreign Minister Kim Gye Gwan publicly rejected U.S. demands to unilaterally abandon Pyongyang's nuclear arsenal and affirmed long-standing regime policy that denuclearization would occur only as part of global arms control initiatives.

While Korea watchers have long known of the strong conditionality that Pyongyang attaches to its nuclear programs, Kim's declaration -- and the significant divergence from the U.S. position -- came as a surprise to the White House.

Faced with the realization that the summit was less likely to produce a breakthrough success, Trump became more ambivalent about attending.

Trump's announcement caught South Korea by surprise, triggering an emergency midnight meeting of its NSC to "attempt to make sense of what, precisely, President Trump means."

What comes next? In his letter to Kim Jong Un, Trump left the door open for diplomacy. He depicted the summit as "inappropriate at this time" but remained open if Kim "changed your mind [about] this most important summit."

The ball was then back in North Korea's court. Pyongyang responded quickly with a relatively conciliatory message that seemed enough to placate Trump.

Less than 24 hours after cancelling, Trump suggested that the meeting with Kim was back on track. But, now that the clear divisions between Washington and Pyongyang over the terms of denuclearization have become blatantly evident, it will be far more difficult to make progress.

Until North Korea complies with UN resolution requirements to abandon its nuclear and missile programs, Washington should continue its policy of maximum pressure that was instrumental in bringing the regime back to the table.

Contrary to misperceptions that sanctions are "maxed out," the Trump administration could bring even more pressure to bear upon North Korea and foreign enablers of its prohibited nuclear and missile programs.

Despite its "maximum pressure" branding, the Trump administration continues to pull its punches against Chinese financial entities assisting North Korea.

The Trump administration should affirm its resolve to defend U.S. allies and the American homeland but be careful in its messaging to avoid needlessly inflaming an already tense situation.

Washington should also refrain from resuming advocacy for a preventive military strike on North Korea, which would be ineffective and dangerously reckless.

President Trump should proceed carefully if he meets with Kim and review any North Korean offers with pragmatic skepticism.

Having North Korea abandon its nuclear arsenal in the U.N.-required comprehensive, verifiable and irreversible manner must be the priority objective of the summit meeting.

The two leaders should work toward detailed text to clearly delineate requirements, linkages and sequencing of responsibilities, expeditious implementation, and a rigorous verification regime.