听力原文： In an apparent attempt to force direct dialogue with the United States, North Korea threatened on Tuesday to abandon the armistice that ended the Korean War five decades ago, accusing Washington of planning an attack. An unidentified spokesman of the North's Korean People's Army said 'the situation on the Korean Peninsula is getting extremely tense' because of alleged U. S. plans to send in reinforcements and build a naval blockade to prepare for a preemptive (先发制人的) attack. North Korea 'will be left with no option but to take a decisive step to abandon its commitment to implement the Armistice Agreement,' quoted by the North's state-run KCNA news agency．Armed forces of the two Koreas were in the middle of their annual winter training． North Korea threatened on Tuesday to abandon the armistice because they______.