Donald Trump raised the case of jailed Hong Kong democracy campaigner Jimmy Lai in talks with Chinese leader Xi Jinping but was told it “is a tough one”.
Family and supporters of the 78-year-old British citizen had hoped the US president could help secure his release.
Lai was sentenced to 20 years in prison in February under a security law imposed by Beijing.
The media tycoon, who was an influential figure in the former British territory’s pro-democracy movement, was arrested in 2020 in a crackdown after massive anti-government protests.
Lai’s legal team says he has health problems, fuelling fears he may die behind bars.
Speaking onboard Air Force One as he returned from his two-day visit to China, Trump said he believed Xi was seriously considering freeing a church pastor detained in China, but was less hopeful over the plight of Lai.
Trump said: “I did bring it up, but it’s a tougher one for him. He said Jimmy Lai is a ‘tough one’ for him.”
In an interview with Fox News broadcast later, Trump said: “I bought up Jimmy Lai. I would say the response to that was not positive.”
He added: “I did not feel optimistic.”
Lai’s daughter Claire said she was grateful to Trump for his commitment to her father’s release.
She said: “He has earned his reputation as liberating the unjustly detained and I am confident he and his administration will be the ones to free my father.”
She added it was an opportunity for Xi to do “the only just and honourable thing”.
Lai, a diabetic, has been kept in solitary confinement without air conditioning in a jail where summer temperatures rise to 44C (111F), his children have said.
“He has lost a very significant amount of weight, visibly, and he is a lot weaker than he was before,” Claire said in remarks to media earlier this year.
“His nails turn almost purple, gray and greenish before they fall off, and his teeth are getting rotten.”
At the end of last year, Trump told reporters he had spoken to Xi about releasing Lai.
“I feel so badly. I spoke to President Xi about it, and I asked to consider his release,” Trump said, without specifying the date he had asked Xi. “He’s an older man and he’s not well. So I did put that request out. We’ll see what happens.”
Lai’s case has sparked international concern, particularly in the UK, where he is seen as being punished for defending democratic undertakings given in 1997 with the handover of Hong Kong from British to Chinese rule.