Caitlin Hayden, an NSC spokeswoman, said Newman has health problems, CNN reported. His family says he has a heart condition and his son said family members are unsure if he received medication to be delivered by Swedish diplomats in Pyongyang.
North Korean officials say Newman has confessed to espionage and war crimes.
Newman, 85, of Palo Alto, Calif., has been held in North Korea since being taken off a plane Oct. 26 as he prepared to leave the country after a 10-day tourist visit, the BBC reported Saturday.
He and a fellow retiree traveled with two Korean guides on a trip organized by a travel service based in London, The New York Times reported.
The official Korean Central News Agency published what it termed Newman's "statement of apology" for ordering the deaths of North Korean soldiers and civilians during the Korean War, and released a video, dated Nov. 9, in which Newman is seen reading the purported apology and requesting forgiveness in disjointed English.
Authorities have previously been accused of coercing confessions from detainees, and the alleged confession may have been a precondition for Newman's release from North Korea without formal legal proceedings, the BBC said.
The U.S. State Department had no immediate comment.
Newman's family in California called the incident "some dreadful misunderstanding," noting he may be in need of medication and noting North Korea may have him confused with an American soldier with another of the same name, who earned a Silver Star during the war.