Both President George H.W. Bush and former first lady Barbara Bush are now in a Houston hospital and will not attend Friday's inauguration of President-elect Donald Trump.

The 92-year-old former president on Wednesday was moved to intensive care at Houston Methodist Hospital after being admitted on Saturday, his office said in a statement.

"Shortly after our previous report on President Bush’s condition, he was admitted to the ICU at Houston Methodist Hospital to address an acute respiratory problem stemming from pneumonia," the statement read. "Doctors performed a procedure to protect and clear his airway that required sedation. President Bush is stable and resting comfortably in the ICU, where he will remain for observation."

Barbara Bush, 91, was admitted Wednesday morning as a precaution after experiencing fatigue and coughing, officials said in a statement.

The 41st president previously sent a letter to Donald Trump expressing his regrets he could not attend Friday's presidential inauguration, adding he and the former first lady "will be with you and the country in spirit."

In his letter -- penned Jan. 10, before he was hospitalized Saturday for breathing problems -- the former president quipped, "My doctor says if I sit outside in January, it likely will put me six feet under."

"So I guess we're stuck in Texas," wrote Bush. "I want you to know that I wish you the very best as you begin this incredible journey of leading our great country," he wrote. "If I can ever be of help, please let me know."

Bush is the father of former President George W. Bush and former Florida Gov. Jeb Bush, who ran in a heated -- and, at times, contentious -- contest against Trump in the 2016 Republican presidential primaries.

Jeb Bush will not be attending the inauguration, but George W. and former first lady Laura Bush will be in attendance, as will Bill and Hillary Clinton.

The elder Bush, who served as U.S. president from 1989 to 1993, has a form of Parkinson's disease and uses a motorized scooter or a wheelchair for mobility. He was hospitalized in Maine in 2015 after falling at his summer home and breaking a bone in his neck, and was hospitalized 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.

Despite the loss of mobility, he celebrated his 90th birthday by making a tandem parachute jump in Kennebunkport. Last summer, Bush led a group of 40 wounded warriors on a fishing trip at the helm of his speedboat, three days after his 92nd birthday celebration.

The Associated Press contributed to this report.