President Barack Obama has praised George W Bush at the dedication of the former president's library for showing strength and resolve in the days after the September 11 attacks and said if Congress passes immigration reform "it will be in large part thanks to the hard work" of his predecessor.
Mr Obama spoke along with all four living former presidents in a rare reunion honouring one of their own at the opening of the George W Bush Presidential Centre.
Mr Bush, the country's 43rd president, gave a closing speech with tears welling in his eyes.
"My deepest conviction, the guiding principle of the administration, is that the United States of America must strive to expand the reach of freedom," Mr Bush said. "I believe that freedom is a gift from God and the hope of every human heart."
The presidents - Mr Obama, Mr Bush, Bill Clinton, George HW Bush and Jimmy Carter - were cheered by a crowd of former White House officials and world leaders as they took the stage together to open the dedication. The leaders put aside the profound ideological differences that have divided them for years.
"To know President George W Bush is to like him," Mr Obama said. He said Mr Bush started an important conversation by speaking about the United States as a nation of laws and a nation of immigrants and he hopes Congress will act this year to pass reform, which Mr Bush was not able to achieve.
For Mr Bush, 66, the ceremony marked his unofficial return to the public eye after the end of his deeply polarising presidency. "Oh happy day," Mr Bush said as he took the stage.
His father, former President George HW Bush, who has been treated in hospital recently for bronchitis, spoke haltingly for just about 30 seconds while seated in his wheelchair, thanking guests for coming out to support his son. A standing ovation lasted nearly as long as his comments.
President Jimmy Carter praised Mr Bush for his role in helping secure peace between North and South Sudan in 2005 and his approval of expanded aid to the nations of Africa.
Among the foreign leaders invited were former UK prime minister Tony Blair, former Israeli prime minister Ehud Olmert and former Italian prime minister Silvio Berlusconi.