President Donald Trump's administration is pushing forward with plans for a historic nuclear summit with North Korea's Kim Jong Un, but some in Washington are concerned by Pyongyang's silence on the idea.
Trump couched his decision to attend talks before the end of May as accepting an invitation from Kim's regime, but the message was passed to the White House second-hand, by South Korean envoys.
Ten days later, Trump seems convinced that the apparent breakthrough came as a result of his "maximum pressure" campaign of diplomatic and economic isolation and warnings of potential military action.
But if Kim is genuinely prepared to discuss the US end goal of the "complete, verifiable and irreversible denuclearization of the Korean Peninsula," he has been very discreet about it.
In private, American officials argue that Kim has much to gain in terms of credibility if the summit goes ahead, and some argue this provides a historic opportunity to end the stand-off.
But US experts see that silence as evidence that Kim is seeking to maintain room to maneuver as the summit agenda congeals, and are advising caution.
Abraham Denmark, director of the Asia Program at the Wilson Center, dubbed it "remarkable that North Korea has seen that they need to maximize their flexibility by staying radio silent."
Denmark's colleague at Wilson, former Pyongyang-based reporter Jean Lee, warns that Kim has not even announced to his own people that any summit it happening, suggesting it may be a way off.
"I think we are perhaps getting ahead of ourselves. We still have a long way to go before we see a summit," she said.
- Back-channel talks -
The North's autocratic regime is notoriously secretive, but before Trump's March 8 announcement of a summit in the months to come, Pyongyang had not been shy about its determination to hang on to its nuclear arsenal.
Still, on Friday, the White House reconfirmed Trump's intention to meet Kim -- even though the State Department said it had yet to receive a North Korean invitation.
North Korean officials have travelled to both Sweden and Finland, touted as possible venues for the eventual face-to-face, but the State Department says no serving American officials met them -- given the two sides do not have diplomatic ties.
There have been reports of back-channel contacts between the governments of the kind Rex Tillerson was pursuing before Trump abruptly sacked him as secretary of state last week.
But these appear to concern the fate of three Americans jailed in North Korea.
"We are working to see US citizens who are detained in North Korea come home as soon as possible," a spokeswoman said.
Last week, State Department spokeswoman Heather Nauert insisted that Washington was not worried that Kim has not said directly that he is ready to discuss the North's nuclear disarmament with the US.
"That is the agreement that Kim Jong Un provided to the Republic of Korea," she told reporters.
"That information was presented to us, and so we are going forward in full faith and understanding that a meeting will go forward."
- North-South hotline -
South Korea's Foreign Minister Kang Kyung-wha is one of a string of high-level diplomats involved in a flurry of meetings in Washington and beyond as officials scurry to make the talks a reality.
Her government -- a close ally of the United States but one that has much to lose if the brinksmanship by Kim and Trump leads to war -- sees the talks offer as a ray of hope and plays down worries.
"I think it was an extremely courageous decision on the part of President Trump," Kang told CBS News.
"We believe the North Korean leader is now taking stock ... So, yes we give them the benefit of the doubt and the time that he would need to come out with some public messaging."
No matter what happens, South Korean President Moon Jae-in's outreach to the North -- which laid the groundwork for the reported invitation -- has borne fruit and he now has a direct hotline with Kim.
"This is very significant," said Lee, of the Wilson Center.
"It has been 10 years since a South Korean leader and a North Korean leader have had a direct line of communication."
- 'Spit-shined and polished' -
Former CIA analyst Jung Pak, now a senior fellow at the Brookings Institution, shares the skepticism felt by many in Washington -- and suggests South Korean optimism may have colored their report.
"Policymakers are furiously trying to plan next steps based on a possibly incomplete or false rendering of what happened in Pyongyang," she argued.
She said Moon's team may have "spit-shined and polished" whatever "nuggets they extracted from Kim" in order to interest Washington in joining his diplomatic engagement.
And now, Pak argues, after Trump's surprise decision, Pyongyang may be scrambling to "craft a strategy to exploit the opportunity that fell into their laps."