LONDON — The United Kingdom rolled out the red carpet and all its considerable majesty Tuesday for President Barack Obama, as he and Michelle Obama launched a two-day state visit that will pivot quickly to more sober discussions of the U.S.-Europe alliance.

First, however, the president and the first lady spent the day Tuesday reveling in the kind of pomp and ceremony that the English do better than anyone else, from a formal welcome by colorful guards to an overnight stay at Buckingham Palace and a lavish state dinner.

They arrived at the palace to the cheers of onlookers as they were greeted by Queen Elizabeth II and her husband, Prince Philip. The queen showed the Obamas around their six-room suite in the 775-room palace, a suite last used by the queen's grandson Prince William and his bride on their wedding night last month. "It may not be the same bed," said a palace aide. "It is the same suite."

After meeting briefly with the young newlyweds, the Obamas were formally welcomed outside on the palace's west terrace. Members of the Scots Guards — with their familiar red uniforms and high black furry hats — lined up in front of him while the pipes and drums of the Scots Guards behind them played "The Star-Spangled Banner."

Throughout the ceremony, the brilliant sunlit sky reverberated with the steady cannon pounding out a 41-gun salute.

The two heads of state also exchanged gifts. The Obamas gave the queen a collection of rare memorabilia and photographs highlighting her parents' 1939 visit to the United States. Her late father, King George VI, was the subject of the movie "The King's Speech," which cleaned up at this year's Academy Awards.

The queen gave the Obamas a bound volume of facsimiles of letters from U.S. presidents to Queen Victoria and an antique brooch.

Touring Westminster Abbey later, Obama laid a red, white and blue wreath at the Grave of the Unknown Warrior, which contains the remains of a British soldier that were moved there in 1920 from a World War I battlefield in France.

"Here we pray for all those who have given their lives in the cause of peace," said the abbey's dean, Dr. John Hall.

Hall also led a prayer for the president, the queen and their respective governments. "Give them grace," he said, "wisdom and skill, imagination and energy."

"Amen," he and the Obamas said, their heads bowed.

At the state dinner at the palace, the 170 guests included British airline mogul Richard Branson and American actor Kevin Spacey.

Obama, in white tie and tails, and the queen entered to the sounds of "God Save the Queen," which is the same tune used for "My Country, 'Tis of Thee" in the U.S. The president sat between the queen and Prince Charles' wife, Camilla, the duchess of Cornwall.

Prince Philip escorted Michelle Obama, who was wearing a white gown. Secretary of State Hillary Clinton also attended.

In her toast, the queen said that when the U.S. and the U.K. stand together, "our people and other people of good will around the world will be more secure and prosperous." The bond between the nations, she said, is "tried, tested and, yes, special."

Obama saluted the queen and the "special relationship" between the countries. Quoting Shakespeare, he toasted "This blessed plot, this earth, this realm, this England."

The president will meet Wednesday with Prime Minister David Cameron, and will deliver a speech on the trans-Atlantic alliance to a joint session of Parliament that the White House and analysts said would be the major address of his six-day, four-country trip.

Throughout the day Wednesday, Obama will affirm the key role of European alliances that he's strived to revitalize after they languished in the George W. Bush years, while looking to assure that they can carry their share of the burden in such joint endeavors as the bombing campaign against Libyan dictator Moammar Gadhafi.

With Gadhafi holding on to his office after two months of NATO bombing, the alliance faces questions about how to force him from power. Moreover, allies such as the U.K. face questions about whether they're up to carrying a greater share of sustained campaigns at the very moment that Obama wants Europe to lead more.

Cameron, for example, is slashing defense spending as part of a broad effort to cut budget deficits; that's left the U.K. without the service of an aircraft carrier and many of the trained pilots it might need for a sustained effort against Gadhafi.

Ben Rhodes, a deputy national security adviser to Obama, brushed aside questions Tuesday about the cutbacks.

"A lot of nations are looking at ways to reduce spending," he said. ""We're confident that Europe can continue to play the role that it's played as our principal partner and fundamental security partner in the world, even as, of course, we have a number of very critical security relationships ranging from obviously our Asian allies to Australia to other countries."

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