President Barack Obama ordered flags lowered to half-staff Monday at the White House and all federal buildings in honor of late former first lady Nancy Reagan.
Reagan, who died Sunday at age 94, will be buried alongside her husband former president Ronald Reagan Tuesday at his presidential library overlooking Simi Valley, California.
A fierce protector of her husband and his political legacy, Reagan had outsized influence during her White House years from 1981 to 1989.
Obama and his wife Michelle praised her "proud example" in a statement Sunday, saying she redefined the role of first lady.
Reagan, the 40th US president, suffered from Alzheimer's disease after leaving the White House and went into a long decline, cared for by his wife until his death in 2004.
The Obamas highlighted Nancy Reagan's advocacy "on behalf of millions of families going through the depleting, aching reality of Alzheimer's."
As a "mark of respect" for the former B-movie actress, Obama ordered that flags be flown at half-staff at federal building, military posts, US naval vessels and diplomatic missions until sunset of the day she is buried.