Warmbier was found guilty in March, 2016, of "hostile acts against the state" for his attempt to steal a propaganda poster on his last night in North Korea before a scheduled trip to Hong Kong as part of a study overseas trip sponsored by the University of Virginia.
In February, Secretary of State Rex Tillerson briefed Trump on the Americans held in North Korea.
"We have very few answers", Fred Warmbier said. Doctors say he has severe injury to all regions of his brain. He said Obama "worked through every avenue available" to try to secure Warmbier's release.
City councilwoman Jenni McCauley said the tight-knit community was "thrilled" to have Otto Warmbier back.
His parents said they learned of their son's condition - what North Korea called a coma - only last week.
Warmbier is a University of Virginia student who arrived back home in OH on Tuesday in a coma. The state-run Korean Central News Agency on Thursday didn't comment on his medical condition.
He was returned to the USA this week after 17 months in captivity, but a significant portion of his brain is damaged after falling into a mysterious coma.
However, doctors said there were no signs of botulism, a condition often associated with contaminated food, which can cause the nerves not to function properly and basically, leads to paralysis in some muscles.
His father, Fred Warmbier, said the family was proud of him, calling him "a fighter".
He arrived in the USA on Tuesday and is stable but "shows no sign of understanding language, responding to verbal commands or awareness of his surrounding", said Dr Daniel Kanter, medical director of the neuroscience intensive care unit at the University of Cincinnati Medical Center, on Thursday.
The doctors said Warmbier's severe brain injury was most likely - given his young age - to have been caused by cardiopulmonary arrest cutting the blood supply to the brain.
They said his prognosis remains confidential. "It was only a week ago that we were informed that the North Korean government now claims he was in a coma for nearly all of that time".
Ellie Boettcher, a 14-year-old rising freshman at Wyoming High, where Otto Warmbier's sister will be a sophomore, said students were elated.
White says Warmbier was a master at defusing tense situations with his humor. A student at the University of Virginia, he had flown to the North that January as a tourist. "But I did take the call, and it was gracious, and it was nice, and I thank him for that".
Doctors plan a news conference on campus later Thursday.
Earlier Thursday, his father told reporters he rejected the regime's explanation that Otto fell into a coma after contracting botulism and taking a sleeping pill in March 2016, shortly after he stood trial in the country for a "hostile act".
The U.S. government never contacted him, said Gratton, a sales manager in his mid-40s who kept in touch with Warmbier's family. His family asked his doctors to disclose details about his condition amid intense scrutiny and questions about his condition. Warmbier was immediately driven to University of Cincinnati Medical Center.
He said Otto "is not in great shape right now" and that his family is "adjusting to a different reality".
"U.S. citizen Otto Frederick Warmbier, who had been in hard labor, was sent back home on June 13 on humanitarian grounds according to the adjudication made on the same day by the Central Court of the DPRK", the statement read. A Young Pioneer Tours official told a news site that focuses on the region that only one person - Otto Warmbier - has ever been arrested among the 8,000-plus worldwide travelers who have taken part in the company's tours. It was the last time he was seen publicly before this week.
He was medically evacuated from North Korea and arrived in Cincinnati late Tuesday. He was then taken by ambulance to a hospital.