Former US president George HW Bush, who has pneumonia, remains in a stable condition in hospital, while his wife Barbara said she is feeling "1,000% better" after undergoing treatment for bronchitis.

Bush spokesman Jim McGrath said the 41st president's doctors are "actively evaluating him" for removal of a breathing tube that was inserted on Wednesday in a procedure to clear his airway.

Mr Bush has since been in the intensive care unit, relying on a ventilator to breathe.

Removing the tube - known as extubation - would allow the 92-year-old to breathe on his own.

He was struggling to breathe when he was admitted to Houston Methodist Hospital on Saturday.

"President Bush had a good night's rest," Mr McGrath said. "We are hopeful he will be discharged from the ICU in a few days."

Barbara Bush, 91, was admitted on Wednesday and diagnosed with bronchitis after feeling fatigued and coughing for weeks.

But she "reports she feels '1,000% better' this morning. Antibiotics and some good rest seem to have restored her to better health", Mr McGrath said.

The Bushes are "deeply appreciative" of the care they are receiving and the "prayers and good wishes from far and wide", he said.

President-elect Donald Trump and President Barack Obama have sent their well wishes, via Twitter and a news conference respectively.

Former president Bill Clinton also tweeted: "41 and Barbara - thinking about you both and sending wishes for a speedy recovery. Love, 42."

Mr Bush's office announced earlier this month that the couple would not attend Mr Trump's inauguration because of the former president's age and health.

His son George W Bush, the 43rd president, still expects to attend the inauguration, spokesman Freddy Ford said.

Even though he was in hospital, the elder Bush's Twitter account was active on Thursday, offering "hearty congrats" to former Houston Astros baseball player Jeff Bagwell on his election to the baseball Hall of Fame.

Mr McGrath said while Mr Bush did not physically type the tweet, he did approve it from his hospital room, calling the Astros' former slugging first baseman a "good friend and great player" and that his election on Wednesday to Cooperstown is well deserved.

Mr Bush was also a first baseman when he attended Yale, and was captain of the Yale team that played in the first College World Series in 1947.

As president, he kept his first baseman's glove in his desk in the Oval Office, and he and his wife have frequently attended Astros games since he left the White House.

The Bushes were married on January 6 1945 and have had the longest marriage of any presidential couple in American history.

At the time of their wedding, he was a young naval aviator. She had been a student at Smith College.

After the Second World War, they moved to the Texas oil patch to seek their fortune and raise a family.

It was there that George Bush began his political career, representing Houston for two terms in Congress in the late 1960s and early 1970s.

Mr Bush, who served as president from 1989 to 1993, has vascular parkinsonism, a rare syndrome that mimics Parkinson's disease, and uses a motorised scooter or a wheelchair for mobility.

He was taken to hospital in 2015 in Maine after falling at his summer home and breaking a bone in his neck.

He was also taken to hospital in Houston the previous December for about a week for shortness of breath.

He spent Christmas 2012 in intensive care for a bronchitis-related cough and other issues.

George Herbert Walker Bush, born on June 12 1924 in Milton, Massachusetts, also served as CIA director and Ronald Reagan's vice president.

George W Bush was elected president in 2000 and served two terms.

Another son, Jeb, served as Florida governor and made an unsuccessful bid for the Republican nomination in 2016.

Only one other US president, John Adams, had a son who also became president.