President Park Geun-hye might not have expected North Korea to immediately show a positive response to a package of proposals for enhancing inter-Korean cooperation and exchanges that she unveiled during her visit to Germany last Friday. Nevertheless, the course of action taken by Pyongyang following her initiative seemed beyond what she and her aides had anticipated.

The North on Tuesday made scathing verbal attacks on Park as it downplayed her proposals. The harshly worded diatribe by the Rodong Sinmun, an official mouthpiece of the ruling Workers’ Party, comes as Pyongyang has upped the ante in its provocative rhetoric and acts. It staged a live-fire drill near the western maritime border Monday, which sent artillery shells into southern waters, prompting the South Korean military to take countermeasures. A day earlier, North Korea threatened to conduct a “new form” of nuclear test in response to a U.N. condemnation of its recent ballistic missile launches.

The North test-fired two ballistic missiles into the sea off its east coast last Wednesday after launching a series of shorter-range missiles and rockets over the preceding weeks. The show of force seemed mainly aimed at countering the ongoing annual joint military exercises between South Korea and the U.S., which are to continue until mid-April. Pyongyang also used the South Korean Navy’s seizure of a North Korean fishing boat that drifted south of the maritime border as an excuse for Monday’s live-fire drill.

But its latest moves can be seen partly as a show of dissatisfaction with Park’s proposals, which fell short of the expectations of the North Korean leadership. Pyongyang seems to be ratcheting up tensions in a measured way to put pressure on Seoul to be more concessionary in future inter-Korean dealings. In this regard, it is noteworthy that the North took the unprecedented measure of giving prior notice to the South about the planned firing drills to keep vessels from entering the training zone.

Pyongyang may also have the more fundamental intention of pushing Seoul and Washington to drop or ease their demand that the communist regime take concrete steps toward denuclearization before the six-party talks, which also involve China, Japan and Russia, are resumed to discuss the dismantling of its nuclear weapons program. North Korea on Monday reiterated it would stick to the policy of developing its economy and nuclear arsenal simultaneously.

Thus, the North may attempt to make further provocations, especially in the period before U.S. President Barack Obama’s visit to Seoul scheduled for late April.

These circumstances require Seoul to tighten its security posture and exercise the wisdom needed to carry forward inter-Korean ties amid Pyongyang’s intransigence toward denuclearization. Close coordination should be maintained with the U.S., which might feel uneasy with South Korea’s possible moves to ease its stance on the North in line with Park’s proposals. China, which immediately voiced concerns over the exchange of fire between the two Koreas, is urged again to use its substantial leverage over the North to stabilize the situation on the peninsula.

North Korea should also recognize that carrying its brinkmanship too far ― with a fourth nuclear test, for instance ― could push it over the cliff this time.