SEOUL, South Korea — North Korea on Monday canceled the armistice agreement that nearly 60 years ago brought a cease-fire to the Korean War, leaving a world of analysts wondering how far the secretive police state will go to show its displeasure with South Korea and its American ally, which still has 28,500 troops based here.

The move, reported by the official Rodong Sinmun newspaper, was anticipated — Pyongyang had said last week that it intended to do so in the wake of new U.N. sanctions over its nuclear weapons program. But the ramifications of the development — the papers cited a military spokesman as saying the armistice had been “scrapped completely” — are far from clear.