Bill Clinton visits George Bush in Houston

Former US president Bill Clinton has been spending some time with former president George H. W. Bush and wife Barbara in Houston.

In a tweet on Sunday, Clinton said they "caught up about kids, grandkids, old times and new times. And socks."

Clinton also showed a photograph of him giving pairs of socks to the 92-year-old former president, who is seen sitting in a wheelchair.

In January, Bush was hospitalised for two weeks for treatment for pneumonia.

Bush has a form of Parkinson's disease and uses a motorised scooter or a wheelchair for mobility. He served as president from 1989 to 1993.