WASHINGTON -- The White House on Thursday declined to confirm reports that three American detainees in North Korea have been released or will be during the day.

The detainee issue is widely expected to be resolved ahead of a planned meeting between US President Donald Trump and North Korean leader Kim Jong-un.

"We can't confirm the validity of any of the reports currently out about their release," White House press secretary Sarah Sanders said during a regular news briefing. "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."

The US citizens -- Kim Hak-song, Tony Kim and Kim Dong-chul -- have been held in the North on charges of espionage or "hostile acts" against the regime.

According to a South Korean activist who cited a Pyongyang resident, the three were moved from a labor camp to a hotel near Pyongyang in early April by order of superior authorities.

Trump hinted at the possibility of their release on Wednesday, tweeting, "As everybody is aware, the past Administration has long been asking for three hostages to be released from a North Korean Labor camp, but to no avail. Stay tuned!"

And on Thursday, Rudy Giuliani, a member of Trump's legal team who is not employed by the government, said the release could happen within the day.

"We got Kim Jong-un impressed enough to be releasing three prisoners today," he told Fox News.

Trump and Kim are expected to meet by early June to discuss the denuclearization of the regime. An announcement on the date and location will likely come within days, the US president has said.

North Korea has a track record of using hostages to force the US to open bilateral talks.

Former US Presidents Bill Clinton and Jimmy Carter traveled to Pyongyang after they left office to win the release of American detainees.

In the latest case, then-US nuclear envoy Joseph Yun went to Pyongyang in June to bring home Otto Warmbier, an American college student who was detained for allegedly removing a political poster from a hotel in Pyongyang.

Warmbier was found to be in a coma, and died shortly after returning to the US.(Yonhap)