(Reuters) - Doctors may move former U.S. President George H.W. Bush out of the intensive care unit of a Houston hospital in the next day or two, with his vital signs returning to normal after a week-long bout with pneumonia, a spokesman said on Sunday.

Bush's wife, Barbara, who had also been admitted to Houston Methodist Hospital last week with bronchitis, has elected to stay one more evening to be closer to her husband, spokesman Jim McGrath said in a statement. Barbara Bush, 91, had the option to be discharged on Sunday,

Bush, 92, who was in the White House from 1989 to 1993, is the nation's oldest living former president. He could not attend Friday's presidential inauguration of fellow Republican Donald Trump because of his health, McGrath said earlier.

Bush, who did not endorse Trump's candidacy, was the only living former president to miss the Washington ceremony. His son George W. Bush, another former president, attended.

Another one of his sons, former Florida Governor Jeb Bush, ran unsuccessfully against Trump last year for the Republican presidential nomination.

The elder Bushes marked their 72nd wedding anniversary on Jan. 6.

(Reporting by Frank McGurty in New York; Editing by Peter Cooney)