According to specialists the next 24 hours will be decisive. By this evening it should be clear whether the swelling of his brain, which followed the stroke, will start to abate. If it does not, his condition could prove fatal.
As Mr Nixon battled for life, his only visitors were his daughters Julie Eisenhower and Tricia Cox, and the evangelist Billy Graham. Mr Nixon's wife, Pat, died last year. Messages of support continued to pour into the hospital and into the Richard M Nixon Library at Yorba Linda, California.
In Washington, President Clinton opened his news conference on Bosnia by saying that he and his wife were praying for Mr Nixon's recovery. Mr Clinton spoke of the 'wise counsel' he had received 'on Russia and many other issues' from the former president.
Mr Nixon's state is caused by cerebral oedema, which routinely occurs after a stroke, and normally begins to diminish after three or four days. But, even assuming this happens, a return to full health is unlikely. Mr Nixon has not been placed on the kind of respirator often used for patients in his condition because it would be against his previously expressed wishes, according to a health worker quoted in the New York Times.
Boris Yeltsin, the Russian president, who snubbed Nixon last month during his visit to Russia because of his meeting with opposition leaders, wished him a speedy return to good health. 'I hope you recover and return to the rough and tumble of political life,' Mr Yeltsin said in a telegram.
The Chinese foreign ministry described Mr Nixon as 'an old friend of the Chinese people'.