The release of three Americans held prisoner in North Korea is being hailed as a sign of increased goodwill heading into next month's U.S.-North Korea summit, but a leading group assisting persecuted Christians is imploring the Trump administration to make human rights and religious freedom an important part of the conversation as well.

President Trump and North Korean dictator Kim Jong-Un are scheduled to meet June 12 in Singapore. Removing nuclear weapons from the Korean peninsula is the top goal for the U.S.

Such an idea seemed impossible just months ago when Trump and Kim were trading barbs about the size of their nuclear buttons, but relation appear to be thawing after Kim's promise to halt testing of nuclear weapons and missiles leading up to the summit, a positive meeting between Kim and South Korean President Moon Jae-in, and now the prisoner release.

Open Doors USA President and CEO Dr. David Curry is also excited about the possibility of North Korea mending its ways.

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"It's likely a charm offensive, but you must acknowledge that progress has been made that hasn't been made before," said Curry.

Open Doors USA assists persecuted Christians around the world. It consistently ranks North Korea as the worst nation on earth in its treatment of believers. Curry says the release of the three Americans ought to remind us that thousands of unknown North Koreans are imprisoned for their faith with virtually no present hope for release.

"I think what it points to is the people that we don't know, the ones that are not American citizens, the 50,000 or more...who are Christians in labor camps right now in North Korea today. They could fill a stadium in any city across America," said Curry.

Curry is pushing the U.S. to demand transparency from North Korea on the treatment of religious and political prisoners.

"What we think would be a helpful thing for the North Korean regime to do - during this time of talk of denuclearization - is make a show of goodwill and open up the labor camps for inspection by the Red Cross so we can begin to understand the scope of the humanitarian crisis there," said Curry.

He expects Kim to resist such a demand vigorously.

"I think Kim Jong-Un will hold out for the lifting of economic sanctions and denuclearization and try to maintain an iron fist control over his regime," said Curry.

That iron-fisted approach can land believers in prison or labor camps for the simplest of things.

"You can be arrested and put in a labor camp for years or decades, and some people even die there just for being caught with a Bible or being under suspicion of being a Christian. If people sense that you've had a Bible study or met with others, these sorts of things in North Korea can get you in a great deal of trouble," said Curry.

Curry says including the issue of human rights and religious freedom is vital for countless people unjustly jailed in North Korea.

"The reason you bring in these human rights issues is that if you really and truly do have 50,000 Christians in labor camps - but there are many more than that for other crimes against the state - what are their conditions? Can we bring the Red Cross and the U.N. into these camps to make sure that people who are starving there can be helped in some way?" asked Curry.

He says the onus is on Kim to prove the international community ought to have a change of heart about his regime.

"What he may not have calculated and what we must insist upon is that if he wants to be part of the international community...and what that means, he's going to have to pass some social norms regarding human rights regarding religious liberty and the treatment of prisoners," said Curry.

And he has other ideas to follow up on those human rights conditions.

"I think an easy one is to allow a visit of the International Religious Liberty Ambassador Sam Brownback within the first 90 days. There are targets I think we can set out like that within 60 days, within 90 days, where the religious liberty ambassador can get in there, have conversations, and have religious liberty, make some observations.

"You have the U.N. Council on Inquiry be able to inspect certain areas, begin to understand how far we have to go with the North Korean regime and what they're willing to do to [allow] the World Health Organization and so forth to aid their people," said Curry.