(Reuters) - The planned summit between U.S. President Donald Trump and North Korean leader Kim Jong Un has raised a California son’s hope that a meeting will lead to the release of his father, held nearly a year by the reclusive state, the son said on Sunday.

Tony Kim, one of the three Americans being held captive by North Korea, is seen in this handout 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

Trump agreed on Thursday to accept an invitation from the North Korean leader to meet by May following months of tough talk by both men and rising tensions over Pyongyang’s advancing nuclear and missile programs.

Three Americans are being held by North Korea, which has in the past used visits by former U.S. presidents Jimmy Carter and Bill Clinton to release other Americans it had in custody.

While there has been no sign the planned summit will lead to the release of Americans Kim Dong Chul, Kim Hak Song or Kim Sang-duk, also known as Tony Kim, word of the unprecedented talks was welcomed by Sol Kim, the son of Tony Kim.

“I am hopeful. It is hard to say any other feeling,” Sol Kim, a 27-year-old student in California, said in a telephone interview.

U.S. officials have previously assured him his father’s plight will be raised at appropriate times, he said.

“But as a family member, I hope that it is one of the top priorities” of a face-to-face meeting, he said.

The U.S. government has had regular talks with the family but has not contacted them since the plans for the summit were announced, he said.

Over the last two decades, North Korea has held more than a dozen Americans as captives, typically using them as bargaining chips in its dealings with Washington.

‘ATROCITIES’

But that dynamic changed after U.S. student Otto Warmbier, 22, died last summer shortly after his release from a 17-month detention.

His death led to new U.S. sanctions on North Korea, and a White House official said it served “to remind the world of the atrocities that happen in North Korea.”

Tony Kim, 59, worked at the foreign-funded and Christian- affiliated Pyongyang University of Science and Technology. He was detained at Pyongyang International Airport in April 2017 while trying to leave the country. North Korean state media reported that he was arrested for committing “hostile acts” against the government.

Kim Hak Song, thought to be 55, also taught at PUST. He managed the school’s experimental farm and was detained in May 2017 while traveling by train from Pyongyang to Chinese border town Dandong

A message attributed to him from 2015 on the website of a Korean-Brazilian church in Sao Paulo said he was a Christian missionary trying to help the North Korean people learn to become self-sufficient.

Kim Dong Chul, a Korean-American missionary formerly of Fairfax, Virginia and thought to be 62, was sentenced in March 2016 to 10 years of hard labor for subversion. Kim said he set up a business in the North Korean special economic zone of Rason in 2008, the North’s officials KCNA news agency reported.

Trump’s sudden decision to meet with Kim stunned even members of his own administration. On Sunday, U.S. officials defended the decision and said the United States expects North Korea to halt all nuclear and missile testing in advance of any meeting.

“As a family, any news, any update and any progress is good progress and it is hopeful,” said Sol Kim.