The U.N. Security Council’s latest sanctions against North Korea, which were approved unanimously by its 15 members Tuesday, should signal ― as noted by U.S. ambassador Susan Rice ― that the impoverished regime will have to pay “an increasingly steep price” if it continues confrontation with the international community.

The resolution imposing new penalties against Pyongyang for its long-range rocket launch last month was a compromise between the U.S. and China, which had held weeks of negotiations over the format and intensity of the U.N. response. It is particularly notable that the council expressed its determination to “take significant action” in the event of North Korea going ahead with another rocket launch or nuclear test.

As expected, the North reacted defiantly to the U.N. action, hinting that it could carry out a third nuclear test following its previous detonations of atomic devices in 2006 and 2009. Shortly after the resolution was passed, Pyongyang issued a statement saying there would be no talks on denuclearizing the Korean Peninsula and that it would take physical action aimed at expanding and strengthening its self-defensive military forces including nuclear deterrence.

Intelligence sources here believe North Korea could conduct a detonation at just a few days’ notice at its nuclear test site in the northeast of the country. But as some experts note, it is unlikely that the North will rush for another nuclear test as it may be too soon to play what is seen as its last card.

While raising its defiant rhetoric, Pyongyang is expected to wait and see what lines would be taken by the incoming government in Seoul and the U.S. administration under President Barack Obama, who has entered his second term. President-elect Park Geun-hye has suggested she would be more active than her predecessor Lee Myung-bak in resuming talks with Pyongyang.

The possibility of the U.S. changing its approach toward North Korea has been raised since Obama recently nominated figures supporting direct talks with the isolated regime as his next secretaries of state and defense. Both Park and Obama, however, have drawn a clear red line the North should not overstep, warning against further provocative acts.

Pyongyang should recognize that the changing external environment could lead to an opportunity for taking steps toward reform and openness. But going for further nuclear tests or missile launches would irreversibly shut it off from the outside world, heightening international voices for its regime change.

Seoul and Washington need to strengthen cooperation with Beijing to ensure the effectiveness of the expanded sanctions and prevent North Korea from conducting a third nuclear test or making other provocative acts. The North must have been upset with China, its only major ally, backing the resolution. China is urged to go this time so far as to get its recalcitrant neighbor to fully realize what the steep price for its continuous unruly behavior would be like.