WASHINGTON (Reuters) - The White House said on Thursday it would welcome the release of three Americans imprisoned in North Korea as a goodwill gesture before a planned summit between U.S. President Donald Trump and North Korean leader Kim Jong Un, but that it could not confirm reports that they are about to be freed.

Expectations have grown that North Korea would soon release the three ahead of the unprecedented summit in the coming weeks.

Rudy Giuliani, Trump’s new main lawyer, told Fox News Channel that Pyongyang would release them as early as Thursday.

It was not immediately clear whether Giuliani had direct knowledge of negotiations around the issue.

CNN, citing an unnamed source, said on Thursday the prisoners’ release was imminent, adding the groundwork for the move was laid two months ago when North Korea’s foreign minister traveled to Sweden and proposed the idea.

“We can’t confirm the validity of any of the reports currently out about their release, but 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,” White House spokeswoman Sarah Sanders told reporters.

The three are Korean-American missionary Kim Dong Chul, arrested in 2015; Kim Sang-duk, also known as Tony Kim, who spent a month teaching at the foreign-funded Pyongyang University of Science and Technology (PUST) before he was arrested in 2017; and Kim Hak Song, who also taught at PUST and was detained in 2017.

Trump did not mention Korea or the prisoners when he spoke at a prayer event at the White House on Thursday. “Our country is doing very well. You’ll see some very good announcements very shortly,” he said.

On Wednesday, Trump said on Twitter, “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!”

Tony Kim, one of the three Americans being held captive by North Korea, is seen in this photo taken in California in 2016, released to Reuters by the family of Tony Kim March 11, 2018. Courtesy of the family of Tony Kim/Handout via REUTERS

But of the three, only Kim Dong Chul was arrested before Trump became president in January 2017.

The U.S. government is looking into reports that the Americans had recently been relocated from a labor camp to a hotel near Pyongyang, a U.S. official said on Wednesday.

The summit between Trump and Kim is expected to take place in late May or early June.

DENUCLEARIZATION

In preparing for the summit, Trump’s administration has said it wants North Korea’s “complete, verifiable, and irreversible denuclearization” but has offered few details of the strategy it will employ at the talks.

Kim told the Chinese government’s top diplomat, State Councillor Wang Yi, on Thursday that he is committed to denuclearization, China’s foreign ministry said, as diplomatic efforts to bring lasting peace to the Korean peninsula gather pace.

“Kim Jong Un said achieving the denuclearization of the peninsula is the firm position of the North Korean side,” China’s foreign ministry said after Wang met Kim in Pyongyang.

North Korea announced on Sunday that it would close its main nuclear test site next month but some U.S. officials are skeptical that Pyongyang will give up its nuclear arsenal.

Trump has promised to ensure that North Korea does not get the capability to build a nuclear bomb that can hit the mainland United States.

U.S. Vice President Mike Pence is postponing his plans to travel to Brazil this month in order to ensure foreign policy resources are focused on Trump’s talks with Kim, Pence’s spokeswoman said.

The exact date and location has yet to be fixed for the meeting between Trump and Kim, who lobbed personal insults and lambasted each other last year over North Korea’s nuclear arms ambitions.

The change in tone has been helped by last week’s meeting between Kim and South Korean President Moon Jae-in, at which the two pledged to work for “complete denuclearization” of the Korean peninsula. Trump said he would maintain pressure on Pyongyang through sanctions ahead of his own meeting with Kim.

Even as Washington presses for the release of the three American prisoners, the parents of a U.S. college student who died last year soon after being release from captivity in North Korea have sued Pyongyang over their son’s death, saying Otto Warmbier was “brutally tortured and murdered.”

Warmbier’s parents told a meeting at the United Nations on Thursday that they would no longer be silent and believed they had to stand up for their son and other families whose loved ones had been abducted by North Korea.

“The only thing we can do is rub their noses in this. It embarrasses them,” said Cindy Warmbier, Otto’s mother. “You can’t negotiate. You just have to shame them.”