George H. W. Bush is in Methodist Hospital in Houston being treated for bronchitis.
The 88-year-old former president has been in and out of the hospital for the past few weeks, his office said in a statement. He is in stable condition and is expected to be released within the next 72 hours.
"We have kept this quiet out of respect for him," chief of staff Jean Becker told the Houston Chronicle. "This is not a life-threatening illness."
Bush, who served from 1989 to 1993, is the oldest living former president, beating Jimmy Carter by a few months.