Former US president George H W Bush has been moved to an intensive care unit at a Houston hospital with pneumonia, while his wife Barbara has also been hospitalised.
Mr Bush was stable and resting comfortably in ICU after doctors performed a procedure to clear his airway, his office said.
His wife, former first lady Barbara Bush, also was admitted to Houston Methodist Hospital on Wednesday as a precaution after experiencing fatigue and coughing, the office said in a statement.
Bush, who at 92 is the oldest living US former president, has been at the same hospital since Saturday after experiencing shortness of breath, family spokesman Jim McGrath said on Wednesday.
Since then, Bush experienced an "acute respiratory problem stemming from pneumonia" and was sedated for the unspecified procedure, his office said.
He will remain in the hospital's intensive care unit for observation.
Bush is the father of former President George W. Bush and former Florida Governor Jeb Bush, who sought the 2016 Republican presidential nomination.
The eldest Bush, a Republican like his sons, was vice-president during Ronald Reagan's two White House terms before being elected president in 1988. He lost his re-election bid to Bill Clinton, then the Democratic governor of Arkansas, in 1992.