"Finally, detaining an American citizen both limits possible US military escalation and can possibly be used to leverage negotiations if Pyongyang wants to open a diplomatic channel to the U.S".
Trump did not specify what those right circumstances were, but White House Press Secretary Sean Spicer later said the North would have to completely dismantle its nuclear capability, stressing, "Clearly, conditions are not there right now".
"Professor Kim was a man who would call North Korea as his own country".
North Korea has vowed retaliation for an alleged failed assassination attempt against its leader Kim Jong-un.
The chairman appointment in 2016 was a sign Kim was consolidating his power after fully assuming the leadership position in 2012. The 62-year-old naturalized USA citizen, who has been held since October 2015, was sentenced to 10 years of hard labor. North Korea accused Tony Kim of being rebellious to the government.
Analysts say North Korea often attempts to use foreign detainees to wrest outside concessions, which in the past have sometimes involved high-profile American missions sent to secure the release of detainees.More news: Apple quietly acquires Beddit's sleep-tracking monitor and iOS app
Four U.S. citizens are now thought to be in custody in North Korea.
Rice's remarks come after North Korea announced that it had detained another U.S. citizen on Sunday, a professor who worked at Pyongyang University of Science and Technology - this time on suspicion of "hostile acts" against the state, according to North Korea's propaganda news outlet.
And although President Trump tweeted during the campaign that similar detentions would not happen during his presidency, Kim Hak Song is the second American to be detained in North Korea during his time in office.
"I think it's clear that North Korea continues to rise in its level of threat", Gardner told Denver7 after a briefing on North Korea at the end of April. The government said he was arrested for "committing criminal acts".
In a 2015 message on the website of a Korean-Brazilian church in Sao Paulo, Kim Hak-song said he was a Christian missionary planning to start an experimental farm at the Pyongyang school and was trying to help the North Korean people learn to become self-sufficient.
Just a day after his detention was revealed, little is known about Kim Hak Song.