Warmbier's family said North Korea insists the coma was the result of botulism and a sleeping pill.
Kim Dong-chul, a 63-year-old former Fairfax County, Va., resident, was arrested in October 2015, a few months before Warmbier, and accused of espionage and subversion.
Right before he was flown back to the US, the regime revealed he had been in a coma due to botulism since a day after his sentencing in March 2016.
Rodman's North Korea visits over the years have fueled speculation that he could somehow facilitate a diplomatic breakthrough between Pyongyang and Washington.
"I know the answer to that", State Department spokeswoman Heather Nauert said - but then she wouldn't say. "The message is that the only way forward is through engagement", North Korea expert Ken Gause told the Yonhap news agency.
A sales manager in his mid-40s from England, Gratton met Warmbier in Beijing before their flight to North Korea as part of a tour group.
Warriors have 'no doubt' Kerr will coach next season
Some teams wouldn't embrace a guy who came into a situation like ours. "If you want to win, it doesn't matter". The Warriors won 129-120 to win the National Basketball Association championship.
Warmbier appeared at a press conference on February 29, on which he admitted the crime of stealing propaganda material, which, he said, "was aimed at harming work ethic and motivation of the North Korean people". "Can you understand what he did in this country?" They didn't tell my delegation, a private delegation.
This latest visit comes amid high tensions between Washington and Pyongyang following a series of missile tests by the North, which have triggered tightened United Nations sanctions.
Fred Warmbier said he and his wife grew frustrated with the lack of progress and with the Obama administration's instructions not to talk about their son's case publicly out of concern it would upset the North and make a release less likely. Yun is continuing his efforts to have the remaining three hostages released.
But one North Korean custom is living under wartime law, and the U.S. has no formal diplomatic relationship or consulate in the country to advocate for USA travelers.
The North is now holding three other United States citizens. The meeting didn't happen until the beginning of June when the US finally learned Warmbier was in a coma. In an emotional news conference in OH, the father did not demur when asked if Obama could have done more.
"That's the main reason why we're going", Rodman said in a video clip posted on his Twitter.