At the time of his arrest, Warmbier had been on an organized New Year's tour in North Korea, a five-day stopover on his way to Hong Kong for a study-abroad trip. His parents said he's been in a coma for more than a year.
A hospital spokeswoman said Warmbier's family was expected to hold a news conference Thursday morning at Wyoming High School.
The witness also said North Korea authorities did not use force against him, but were tough. He was arrested in January 2016 and accused of trying to steal a propaganda poster from an employee area of his hotel.
The State Department denied any connection between Warmbier's release and Rodman's visit, which the Trump administration said it did not authorise.
The U.S. relies on Sweden to represent its interests in North Korea, since the U.S. has no direct diplomatic relations with North Korea itself. President Donald Trump has been promising to exert "maximum pressure" on North Korea to make it abandon its nuclear weapons program, but has also dangled the prospect of talks with Kim, whom he called a "smart cookie". Yun met North Korea's ambassador to the United Nations on June 6 and was told about Warmbier's condition, the official said, speaking on condition of anonymity. "My Center for Global Engagement has worked on behalf of the Warmbier family with the North Korean government directly, including a visit late previous year to advance negotiations for his release, as well as with both the Obama and Trump administrations". The last instruction the president left Tillerson was: "Take care of Otto", the official said.
He said that Beijing's pledges to clamp down on the North had been "uneven", but added: "They have taken steps, visible steps that we can confirm". 'The only comment I have is that I am very happy that he is on his way home and to encourage folks to continue to pray for Otto and his family, ' Thomas said.
Regardless of how Warmbier's coma began, his prognosis could be grim, given that he has been in a state of unconsciousness for approximately a year. In a statement confirming Warmbier's homecoming, his parents said they were told their son had been comatose since March 2016, the month he was convicted.
In rare high-level contacts, Yun met senior North Korean officials in Oslo in May, where it was agreed Swedish officials in Pyongyang, who handle U.S. consular affairs there, would be allowed to see all four American detainees, a State Department official said.
Rodman said the issue of several Americans detained by North Korea is "not my objective right now", in remarks made in Beijing before the release of Warmbier was publicly disclosed.
War, violence, persecution push displacement to new unprecedented high
South Sudan has the fastest-growing displaced population in the world after peace efforts in the country fizzled out in July. Refugee children from South Sudan walk in Bidibidi resettlement camp in the Northern District of Yumbe on April 14, 2017.
There are now three USA citizens being held in the country.
Warmbier would have graduated in May.
The BBC's Stephen Evans in Seoul says it remains to be seen if Mr Warmbier's illness is the direct result of brutality in prison.
For over a year, Warmbier was deprived of his most basic of human rights as the poor student was innocently caught in the cross-hairs of North Korea's continued acts of provocation against the United States.
In a short statement earlier Tuesday Secretary of State Rex Tillerson announced Otto was coming home.
At least three American citizens are still being held in North Korea.
He added that because America has no trade with North Korea, the most effective way to impose pressure is through "secondary sanctions" that threaten companies from third countries with losing access to the U.S. market if they deal with Pyongyang.
In Tokyo, a visiting senior US official said Rodman is making the trip as a private citizen. FILE - In this January 8, 2014, file photo, former NBA star Dennis Rodman sings Happy Birthday to North Korean leader Kim Jong Un, seated above in the stands, before an exhibition basketball game at an indoor stadium in Py.