(CNN) The status of three Americans detained in North Korea remained unclear on Thursday as anticipation builds over their possible release.

President Donald Trump and his allies outside the government sought to fan the heightened expectations, casting the potential development as evidence of his negotiating prowess ahead of a summit with North Korean dictator Kim Jong Un.

But experts and even some administration aides worried the celebration may be premature and could send the wrong signals to Pyongyang.

Rudy Giuliani, a member of Trump's legal team but not himself an employee of the government, said Thursday morning the release would happen within the day.

"We got Kim Jong Un impressed enough to be releasing three prisoners today," Giuliani said on "Fox & Friends."

Trump, after tweeting about the Americans Wednesday evening with instructions to "stay tuned," said during a Rose Garden event on Thursday that "some very good announcements" would be coming shortly, but did not specify on what.

And an official with knowledge of the ongoing negotiations told CNN the release of the detained Americans is "imminent" following months of talks.

Still working to verify

Inside the White House and State Department, however, officials were still working to verify reports the three Americans had been moved from labor camps to a hotel in Pyongyang. The families of the prisoners, meanwhile, said they had received no new information about their loved ones.

"We can't confirm the validity of any of the reports on their release," White House press secretary Sarah Sanders told reporters Thursday. "We certainly would see this as a sign of goodwill if North Korea were to release the three Americans ahead of discussions between President Trump and Kim Jong Un."

A US official said the administration is "confident" the Americans held in North Korea will be released, but offered no speculation on timing. As of Wednesday evening, the US had not yet received direct confirmation from Pyongyang that the Americans had left the work camps. The Americans' conditions are also unknown, according to the official.

Planning is underway for Trump's closely watched summit with Kim, which is expected to occur by early June. Members of the President's national security team met on Wednesday afternoon to discuss the talks, including their potential location.

Trump has expressed a preference for the inter-Koran Demilitarized Zone, saying if the meeting is successful it would provide a celebratory backdrop. But some of his aides have warned that holding the summit there could appear as if Trump is traveling to Kim's territory instead of meeting on neutral ground, like Singapore.

No final decisions on a date or location for the summit were made at Wednesday's national security meeting, officials said. But the release of the detained Americans would be seen as a positive development ahead of talks.

Frustration

Some members of the administration were frustrated as reports of the American detainees' release seemed to get ahead of official US pronouncements -- fueled partly by the President's own lawyer.

"This isn't how we should be doing this," sighed one US official after Giuliani's appearance on Fox. The official said the administration had hoped any announcement about the Americans' release would come from the President himself.

Sanders said on Thursday that Giuliani does not have wide leeway from Trump to discuss foreign policy, and couldn't answer whether the two men discussed the matter of the American prisoners.

"I'm not aware they spoke about that. I don't know," she said.

Joseph Yun, who until March was the administration's top diplomat working on North Korea issues, said it was "worrisome" that Trump's allies would tout a release before it's complete.

"We really shouldn't be talking about their release, nobody should be talking about their release, until it happens because any kind of real speculation sends the wrong signals and could jeopardize them," said Yun, who is now a CNN global affairs analyst.

Yun traveled to Pyongyang last June to negotiate the Americans' release, but was only successful in securing the handover of Otto Warmbier, an American student who died days after his return to the United States.

The three Americans currently detained -- Kim Dong Chul, Kim Hak-song and Kim Sang Duk, also known as Tony Kim -- have been detained in North Korea for months. Kim Dong Chul has been in North Korean custody since before Trump was elected, and the other two detainees were arrested last spring, after Trump's inauguration and as tensions between Washington and Pyongyang were beginning to ramp up.

Tony Kim and Kim Hak-song, who were arrested in April and May of 2017 respectively, were both accused of carrying out "hostile acts" against the Kim regime. Both worked at the Pyongyang University of Science and Technology (PUST) which bills itself as the only privately run university in the North Korean capital.

Kim Dong Chul was arrested in 2015 for spying on behalf of South Korea, he told CNN in January 2016. The interview was conducted in the presence of North Korean officials, so CNN could not determine whether Kim's comments were made under duress.