"President Bush has had a series of setbacks which, combined with his age, have complicated the timeline for his release," Bush's spokesman Jim McGrath said.
Earlier this month, McGrath said Bush would be released in time to spend Christmas at home, but then the octogenarian suffered a fever last week after feeling weak for a few days.
The spokesman did not provide details of a possible release date.
Bush had served as the 41st president in the White House from 1989 to 1993, commonly known for attacking Iraq during the first Gulf war after Saddam Hussein's forces invaded Kuwait.
Bush is the father of former US President George W. Bush who served as the 43rd president from 2001 to 2009 and has been widely accused of committing crimes against peace and humanity, as well as genocide over his role in the Iraq war.
Former United States President George H.W. Bush has remained hospitalized over the Christmas holiday due to a series of health complications.
The 88-year-old former US president spent Christmas with family members at the Methodist Hospital in Houston, Texas, over a lingering bronchitis-like cough.
Bush had initially been admitted to the hospital on November 7 for bronchitis treatment and released on November 19, but was readmitted on November 23 after persistent complications, lasting ever since.