Nauert said that the administration is "contemplating" restricting American travel to North Korea, but a decision has not been reached.
When Warmbier was first detained in Pyongyang airport allegedly for a "hostile act" - which turned out according to his conviction to be stealing a propaganda poster - there was already another American in North Korean custody.
A North Korean official has indirectly denied any wrongdoing in the handling of Warmbier.
"I have made the worst mistake of my life!" he exclaimed, choking up as he begged to be allowed to reunite with his parents and two younger siblings. His family said it was told he had been a coma since soon after his March 2016 sentencing.
Seoul's Defense Ministry said the bombers engaged in routine exercises with South Korean fighter jets aimed at showing deterrence against North Korea. They said he suffered extensive loss of brain tissue and "profound weakness and contraction" of his muscles, arms and legs.
Given the mystery behind Otto's condition, there's a real possibility that they could wind up in the same situation.
The young man was described as being in a state of "unresponsive wakefulness", opening his eyes but showing no signs of understanding language or of being aware of his surroundings.
Dr. Michael Baden, a Fox News contributor and one of the nation's leading forensic pathologists, says an autopsy may be the only way to determine if the student's coma was the result of botulism and a sleeping pill, as North Korea claims, or a savage beating.
Warmbier, an OH native and student at the University of Virginia, was arrested in North Korea in January 2016 while visiting as a tourist.
They said Warmbier's condition was probably caused by cardiopulmonary arrest cutting the blood supply to the brain.
"President Moon Jae-in expressed regrets after hearing the news of [Otto] Warmbier's death", presidential office spokesman Park Soo-hyun told reporters in comments carried by Yonhap News Agency. It said the flights demonstrated solidarity among South Korea, Japan and the United States "to defend against provocative and destabilizing actions in the Pacific theater".
Trump called the situation a "disgrace" and is now facing calls for the USA to respond to North Korea for its role in Warmbier's death.
The Trump administration is still considering how to respond to the death of 22-year-old Otto Warmbier.
The president says if Otto Warmbier had been returned home to the USA earlier, "I think the result would have been a lot different".
In a statement after his return, his father, Fred Warmbier insisted that North Korea lied and in fact kept his son's state of health secret until he was brought back to the US. "Surrounded by his loving family, Otto died today at 2:20pm". He was traveling in China when he signed up, out of curiosity and a sense of adventure, for a four-day trip to North Korea.