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."
Just spent amazing time with Colbert!
Is he sane? He is cool! #cgiu
The bio on the account, which has already amassed over 56,000 followers, appears to have been heavily influenced by Colbert: "I am President William Jefferson Billy Jeff Rodham Clinton. Stephen Colbert is my BFF." [Best Friend Forever]
The interview filmed on Saturday in St Louis for at the annual Clinton Global Initiative University and has since been promoting Clinton's new Twitter account:
Former US President Bill Clinton said: "I was saddened to learn of the death of Lady Margaret Thatcher. The United Kingdom has lost its first woman Prime Minister, an iconic stateswoman, and a fearless leader.
"The United States has lost one of its dearest friends and most valued allies.
"Lady Thatcher understood that the special relationship which has long united our two nations is an indispensable foundation for peace and prosperity. Our strong partnership today is part of her legacy.
"Like so many others, I respected the conviction and self-determination she displayed throughout her remarkable life as she broke barriers, defied expectations, and led her country.
"Hillary, Chelsea, and I extend our condolences to her family and to the people of the United Kingdom."