WASHINGTON — In a rare public tribute to his predecessor, President Obama unveiled the formal White House portrait of George W. Bush on Thursday, praising his "strength and resolve" after the Sept. 11 attacks.

Obama said Americans never would forget the image of Bush, "bullhorn in hand," standing atop a pile of rubble at the World Trade Center, conveying strength not only to the American people but, on behalf of the country, to the world.

They were the most laudatory words Obama has spoken publicly about Bush, whose record in office and as commander in chief was assailed during Obama's 2008 campaign for president. Obama has continued to blame Bush for the nation's economic problems.

Though unusual, Obama's praise was far from effusive. He mentioned the mission that "delivered justice" to Osama bin Laden, whom Bush pursued in vain throughout his presidency. But Obama tempered those comments by thanking people over the span of "two administrations" who laid the groundwork for the operation.

He also thanked Bush for setting up "a really good TV sports package" for him. "I use it," Obama told the crowd, eliciting laughter.

Bush responded in kind, with a mix of gratitude to Obama and his wife, Michelle, and a series of one-liners about joining a collection of portraits dating to George Washington (the other "George W.," he noted).

"Thanks so much for inviting our rowdy friends to my hanging," Bush said to laughter. He then praised his wife, Laura, his mother, Barbara, and above all his father, former President George H.W. Bush, who attended the ceremony in a wheelchair.

George and Laura Bush then lifted black sheets to unveil a pair of portraits by artist John Howard Sanden. George W. Bush is depicted standing in the Oval Office in front of one of his favorite paintings, "A Charge to Keep," a 1929 Western that he used for the title for his 1999 memoir. Laura Bush's portrait shows her in a midnight-blue gown standing in the Green Room, which she helped refurbish in 2007.

The audience was packed with members of Bush's administration, including Colin Powell (secretary of state), Donald Rumsfeld (defense secretary), Alberto Gonzalez (attorney general) and Andrew Card (chief of staff). Karl Rove, Bush's political mastermind, sat prominently in the second row, exchanging pleasantries with Vice President Joseph Biden.

When Bush played host to former President Clinton for the unveiling of his official portrait in June 2004 — in the heat of another political season — the East Room was filled with veterans of the Clinton administration, a large number of whom were working to oust Bush as members of Sen. John Kerry's presidential campaign.

But relatively few members of Bush's inner circle are working on the campaign of Mitt Romney, the presumptive Republican nominee. Bush has been in a self-imposed political exile, absent from the Republican campaign trail, although he recently offered a fleeting endorsement of Romney.

On Thursday, though, partisanship was banished in favor of gracious pronouncements about the unusual burdens and majesty of the presidency.

"It's wonderful to see because so often in American history, you had presidents hiding the portraits of predecessors they didn't like," presidential historian Michael Beschloss said. "In recent years, instead, this has become a rare presidential ritual of national bipartisanship."

As Obama put it: "We may have our differences politically, but the presidency transcends those differences. We all love this country. We all want America to succeed."

Bush had the last word as he stood looking at his portrait, depicting him in a dark suit, on the verge of his signature grin.

As Obama deals with difficult decisions to come, Bush said he hopes the younger man will wander past the newest portrait and ask himself one question:

"What would George do?" he said, to thunderous laughter.