"My father had just finished his semester as a professor in North Korea when he was arrested at the airport," said Kim's eldest son, Sol, in a YouTube video.

"No explanation was given," Sol added. "My family and I have had no contact with him since."

Kim was a professor at Pyongyang University for Science and Technology, the country's only privately-run academic institution, when he was arrested on April 22, 2017.

"My mom, brother and I miss our dad so much. We are so worried about him and his health."

Kim's family is now hoping president Trump's sudden decision to meet North Korea's dictator Kim Jong Un in an historic US-NK summit will lead to his father's release.

"I am hopeful. It is hard to say any other feeling," the 27-year-old Sol Kim told Reuters.

Sol's father, who taught accounting at the university, was accused of anti-state activities and trying to overthrow the government. He was given a 15-year sentence.

A month later, another instructor from Pyongyang University for Science and Technology (PUST), Kim Hak Song, was also arrested.

A third person, Kim Dong Chul, a Korean-American missionary, was arrested in October 2015 and sentenced in March 2016 to 10 years of hard labor for subversion.

PUST was founded in 2010 by Dr. James Kim, a Korean American Christian businessman, with funding from South Korean and American Christians.

Dr. Kim appeared on CBN's 700 Club in 2011 to explain the mission behind the university.

The surprise announcement last week of a summit has many optimistic about prospects for a diplomatic solution to ending North Korea's nuclear ambitions.

Still, the White House is warning the US will continue to exert maximum pressure on the rogue regime until then. (Screengrab: Sol Kim urges Americans to press congress for help/YouTube)

Sol is hoping for a breakthrough.

"As a family, any news, any update and any progress is good progress and it is hopeful," Sol told Reuters.

The family's ordeal over these past 10 months hasn't been easy.

"These are hard days for our family," Sol said in the video. "My family and I long to make contact with my dad."

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