Just ahead of its fourth nuclear test last month, North Korea had offered bilateral talks on sealing a peace treaty, but the proposal failed to materialize as the U.S. stood by its denuclearization priority, Seoul and Washington officials confirmed Monday.

The overture was reportedly made “days before” the Jan. 6 detonation through the New York channel based in Pyongyang’s permanent mission to the U.N. But their exchanges fell through after the North brushed off the U.S. counterproposal that denuclearization negotiations should come first.

“To be clear, it was the North Koreans who proposed discussing a peace treaty. We carefully considered their proposal and made it clear that denuclearization had to be part of any such discussion,” U.S. State Department spokesman John Kirby said.

“The North rejected our response. Our response to North Korea’s proposal was consistent with our longstanding focus on denuclearization.”

Seoul’s Foreign Ministry said the allies have been in close consultations on their response not only to the communist state’s latest atomic and missile experiments, but also to its calls for a peace treaty.

“South Korea and the U.S. maintain the consistent position that in any talks with North Korea, denuclearization should take priority,” the ministry said in a statement.

The revelation came as Pyongyang’s official media has been churning out reports displaying its willingness to put a moratorium in its nuclear tests in return for a deal that could replace the 1953 armistice reached at the end of the Korean War.

Last week, Chinese Foreign Minister Wang Yi also proposed holding peace treaty and denuclearization negotiations with Pyongyang in tandem, but Seoul and Washington dismissed the idea as they are focusing on slapping sanctions over the recent provocations and steadfast in their disarmament-first principles.

Though South Korea argues they are in “close cooperation” with the U.S. at all times, if Pyongyang manages to make a “forward-looking” overture, turn around the current frosty mood and bring Washington back to the negotiating table, it may deal a blow to the Park Geun-hye administration that has been hardening its line against the wayward neighbor.

Since the Feb. 7 rocket test-firing, it virtually shut the door for dialogue unless the North makes headway in denuclearization, pulling out from a joint factory park and even threatening a “regime change.”

“As we have made clear, denuclearization discussions should be put first, and a peace treaty is not a matter for the U.S. and the North alone. We the South should be in the driver’s seat,” Seoul’s Unification Ministry spokesman Jeong Joon-hee told a news briefing.

By Shin Hyon-hee (heeshin@heraldcorp.com)