The response out of Washington was a brief statement from US Secretary of State Mike Pompeo, who said the US "appreciates the cooperation" of North Korea and Sweden, which facilitated the release.

That stood in stark contrast to May's highly publicized release of three Korean-American detainees from the North, which came ahead of a high-stakes June summit between US President Donald Trump and North Korean leader Kim Jong-un.

Trump not only tweeted that the "3 wonderful gentlemen" were in the air with Pompeo, who traveled to Pyongyang to secure their release, he also greeted them upon their arrival in the early morning hours.

"I think the low-key US response ... may be due to its relatively swift resolution, and the reality that its North Korea policy has pretty much hit a wall," Robert Manning, a senior fellow at the Washington-based Atlantic Council think tank, said in an email to Yonhap. "The diplomatic impasse contrasts with Trump's positive assessment and continued plans for a 2nd Trump-Kim Summit."

The May release was seen as a concession ahead of the first Trump-Kim summit in Singapore, which yielded a commitment from the North to work toward "complete" denuclearization of the Korean Peninsula.

The men had been held by the regime for as long as two years and seven months.

This month's release was also interpreted as a goodwill gesture amid deadlocked negotiations on implementing the summit deal.

While North Korea has increasingly called for sanctions relief in return for steps to dismantle its nuclear weapons program, the US has refused to offer major concessions before the full and verified denuclearization of the regime.

Pompeo could meet with his North Korean counterpart in New York this week, according to some reports that the State Department has declined to confirm. The two were initially slated to meet Nov. 8 before the US announced an indefinite postponement over a scheduling conflict.

"It would seem to me that there is a delicate diplomatic dance going on between the US and North Korea at the moment," Ken Gause, a North Korea expert at CNA Corp., said in an email to Yonhap. "Neither side is willing to fully invest itself in the engagement because both sides are sticking firmly to their positions (denuclearization vs. sanctions relief)."

Gause noted, however, that the Trump administration appears to have backed off its demand for a declaration of North Korea's nuclear arsenal ahead of a second summit and "may have even given its blessing" for a UN sanction exemption that was required for the two Korea to conduct a joint study to reconnect their railways.

"North Korea with this release may also be reciprocating. Both sides (are) seeing if their concessions might bear fruit," he added.

A State Department spokesperson declined to provide information on Lowrance, saying only that any US citizen detained abroad is offered "all appropriate consular assistance."

"We have no further information to share due to privacy considerations," the spokesperson told Yonhap.

Meanwhile, Lowrance is believed to be the same 59 or 60-year-old man who was deported from South Korea in November 2017 after he was caught just south of the heavily fortified inter-Korean border.

He reportedly told South Korean police that he wished to contribute to resolving tensions between the US and North Korea. (Yonhap)