Former US President George HW Bush may not be released from a Houston hospital in time to celebrate Christmas at home as doctors had hoped.

The former leader has been hospitalised for a month and has been undergoing treatment for bronchitis.

Mr Bush, 88, remained in stable condition and doctors were optimistic he would make a full recovery, George Kovacik, a spokesman at Methodist Hospital, said in an emailed statement.

But doctors were being "extra cautious" with his care and no discharge date had been set, the statement said.

Earlier this month, Mr Kovacik said doctors expected Mr Bush would be able to spend Christmas at home with his family.

"His doctors feel he should build up his energy before going home," the statement said.

Mr Bush, the 41st president and a Republican, took office in 1989 and served one term in the White House.

The father of former President George W Bush, he also is a former congressman, UN ambassador, CIA director and vice-president for two terms under Ronald Reagan.