North Korea warned, on Monday, that it would not even consider the release of two jailed Americans if former detainee Kenneth Bae keeps "jabbering" about his imprisonment.
Bae, a South Korean-born American missionary, was arrested in November 2012 and later sentenced to 15 years' hard labour on charges of seeking to topple the North Korean government.
He was released in November 2014, along with one other US detainee, after a secret mission to Pyongyang led by US intelligence chief James Clapper.
Since his release, the 47-year-old has published an account of his time in a North Korean prison and revealed plans to set up a foundation to support North Korean defectors.
"As long as Kenneth Bae continues jabbering, there will be no negotiations on American criminals," said the North's state-run KCNA news agency.
"In that case, the US criminals held in our country will never be able to set foot in their homeland," it said.
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Two US citizens are currently serving prison time in North Korea.
Otto Warmbier, a 21-year-old college student, was sentenced to 15 years' hard labour in March for stealing a propaganda banner from a tourist hotel in Pyongyang.
In April Korean-American missionary Kim Dong-Chul was sentenced to 10 years' hard labour on charges of subversion and espionage.
In the past North Korea has used the detention of US citizens to obtain high-profile visits from the likes of former US presidents Jimmy Carter and Bill Clinton to secure their release.
The United States has no diplomatic or consular relations with the North. The Swedish embassy in Pyongyang provides limited consular services to US citizens detained there.
The US State Department "strongly recommends against all travel" to North Korea and specifically warns of the risk of arrest.