Former US president George HW Bush will stay at a Texas hospital through the weekend after experiencing breathing problems, but his spokesman says he could soon be discharged.

Bush, 90, was admitted late on Tuesday to Houston Methodist Hospital.

He received family visits on Christmas Day, and his spokesman Jim McGrath said he was making progress.

"President Bush's condition has improved to the point that doctors have begun discussing dates for his discharge," McGrath said in a statement.

"He will remain at the Houston Methodist Hospital through the weekend for further observation."

The spokesman did not explain the reasons for the extended stay or give details of when Bush, who uses a wheelchair, would be discharged.

Bush, the oldest of the four living former US presidents, seemed frail in recent public appearances.

He was treated at Houston Methodist in November 2012 for bronchitis, spending nearly two months at the hospital.

The former president's wife Barbara was admitted to the same Houston hospital nearly a year ago.

The former first lady was released from the hospital in January after recovering from pneumonia.

Bush, patriarch of one of America's most prominent political dynasties, is father to former US president George W. Bush.

Another son, Jeb, last week announced that he was laying the foundation for his own 2016 White House bid.