Former US President George H.W. Bush is in the intensive care unit of a Houston hospital following a series of setbacks including a persistent fever.
The 88-year-old was admitted to the hospital on 23 November for bronchitis.
Family spokesman Jim McGrath said Mr Bush was admitted to the intensive care unit at Methodist Hospital on Sunday.
He said the former president was alert and conversing with medical staff, and was surrounded by family.
Mr Bush has lower body parkinsonism, which causes a loss of balance, and has used wheelchairs for more than a year, Mr McGrath said.
A hospital spokesman said in mid-December that Mr Bush was expected to be home from the hospital in time for Christmas, but that spokesman later said doctors felt that the former president should build up his energy before going home, Reuters reports.
The 41st US president and a Republican, he took office in 1989 and served one term in the White House.
The father of former President George W. Bush, he also served as a congressman, ambassador to the United Nations, envoy to China, CIA director and vice president for two terms under Ronald Reagan.