Pyongyang has been concerned that the submission of a list of its nuclear weapons, materials and related sites -- a key denuclearization step demanded by the US -- could be tantamount to making them potential targets for attack absent clear security assurances. 

Taking such a step when the fate of the incumbent US government remains uncertain would be a key concern for the communist regime, a reason why it may now be "taking a breather," the source pointed out. 

The remarks came amid growing concerns that Pyongyang could resume major provocations such as an intercontinental ballistic missile launch in protest over the stalled nuclear talks. 

The source noted that the North may need to restart negotiations to seek sanctions relief for its economic development ahead of big political events next year such as the 75th anniversary of the founding of its ruling Workers' Party. 

North Korean leader Kim Jong-un may also need to secure economic progress next year, the last year of his five-year economic development scheme ambitiously rolled out with a pledge to feed his people well enough to avoid further belt-tightening. 

But the possibility of North Korean provocations remains, putting Seoul officials on alert. 

Pyongyang could engage in rhetorical provocations such as declaring a strengthening of its nuclear capabilities or restarting a key nuclear reactor at its mainstay nuclear complex in Yongbyon, north of Pyongyang. 

It could also declare it would no longer be bound by its self-imposed moratorium on nuclear and long-range missile tests. 

What's more worrisome is the possibility of the North launching physical military provocations such as an ICBM test or a long-range rocket experiment disguised as peaceful space development activity.

The North has warned that it would take a "new way" if the US does not come up with an acceptable new proposal in the negotiations. That new direction is expected to be clarified during a major ruling party gathering this month or in the North Korean leader's New Year's address. 

South Korea's top nuclear negotiator, Lee Do-hoon, is seeking to visit the US next month to discuss a step forward to keep the North on the dialogue track. (Yonhap)