Former US President George HW Bush's fever has worsened with doctors putting him on a liquids-only diet, a spokesman for his hospital in Texas has confirmed.
But Jim McGrath said doctors were "cautiously optimistic" about the course of treatment he is on.
Mr McGrath, who was quoted by the Associated Press, said doctors still do not know what is causing the 88-year-old's "stubborn" fever, despite treating it with Tylenol.
Mr Bush was brought to the Houston hospital for the bronchitis-like cough on November 23.
More top news
Southern areas windy and very mild.
Nobel-prize-winning schoolgirl Malala Yousafzai has said she is a proud Brummie, as a new portrait of her was unveiled in her adopted home.
The Filipino girl group lost out to Lauren Murray in the sing off after receiving the lowest number of votes.