WASHINGTON - What's a couple of centuries between the best of friends?

President Bush, welcoming Queen Elizabeth II to the White House on a resplendent spring morning, was noting yesterday how often the British monarch had visited the United States.

"You helped our nation celebrate its Bicentennial in 17, " said Bush, quickly correcting himself on a bunting-draped stage, " . . . in 1976."

And then, after turning to smile at the queen, the president advised a crowd of several thousand assembled on the South Lawn of the White House: "She gave me a look that only a mother could give a child."

With this unwitting ice-breaker in a formal ceremony steeped in the pageantry of American military honor guards and the red-coated 3rd U.S. Infantry Regiment Old Guard Fife and Drum Corps marching beneath a nearly cloudless sky on a cool and breezy morning, the president opened the White House for a day of feasts that would culminate in a five-course state dinner honoring the royalty of its closest ally, the first white-tie dinner of the Bush administration.

The U.S. and United Kingdom share centuries of history. Queen Elizabeth commemorated the 400th anniversary of the James-town Settlement in Virginia with this, her fifth visit to the U.S. but her first in 16 years.

The erstwhile adversaries, their Colonial ties severed by revolution, stand today as the staunchest allies at war in Iraq and Afghanistan.

Their modern alliance has taken political tolls on the leaders of both nations, with Bush's popularity at home languishing in the fifth year of an unpopular war, and third-term British Prime Minister Tony Blair expected to announce this week that he will resign this year, probably in July.

The gravity of the challenges they face could not be overlooked on the South Lawn.

"Today our two nations are defending liberty against tyranny and terror," Bush said in welcoming the queen. "Our work has been hard. The fruits of our work have been difficult for many to see. Yet, our work remains the surest path to peace."

Still, for those assembled in a ring around the sun-splashed South Lawn, where the Air Force Band struck up the national anthems, pomp reigned over politics. Marine trumpeters played on a balcony of the South Portico framed with planters of red geraniums, and the flags of two nations unfurled in a gentle breeze.

Speaking of her visit, the queen said it was "a brief opportunity to step back from our current preoccupations to reflect on the very essence of our relationship. It gives us the chance to look back at how the stories of our two countries have been inextricably woven together."

With the customary wave of a white glove from a balcony of the South Portico, Queen Elizabeth joined Prince Philip, Bush and first lady Laura Bush for the start of two days of reciprocal entertainment - ending with a dinner tonight for the Bushes at the British Embassy.

This is a queen whom many have known for a lifetime, a queen who would become Britain's oldest monarch by year's end, outliving her great-great-grandmother, Queen Victoria. This is a queen who has dined with 10 American presidents.

Which of course begged the question: What's for dinner?

With 134 guests seated at 13 tables for five courses in the State Dining Room, this would be the first white-tie dinner at the White House since President Bill Clinton hosted Spain in 2000.

"I will tell you that we did have to talk the president into white tie," Laura Bush said, adding that Secretary of State Condoleezza "Rice and I took it upon ourselves to talk him into it. . . . And so he was glad to wear white tie. But I don't know about the rest of our guests, especially the ones from Texas. They're probably having to go out and rent theirs this afternoon."

Dinner guests included Calvin Borel, the jockey on this year's Kentucky Derby-winning Street Sense - a race the queen attended at Churchill Downs.

Peyton Manning, the Indianapolis Colts quarterback, was invited. So was Arnold Palmer, the golfer. Texas oilmen Ray Hunt and Boone Pickens. and NBC newsman David Gregory joined former Secretary of State Henry Kissinger and former first lady Nancy Reagan.

The dinner followed a luncheon of heirloom-tomato fondue, seared baby sea bass and lemony risotto, ruby-red grapefruit and Florida avocados in a citrus dressing, followed by raspberry meringue and chocolate sorbet.

After lunch, the president and first lady escorted the royal couple to the president's official guesthouse, Blair House, across the street, stopping long enough outside the front gate of the White House for the queen to sign autographs for children and for the president to receive a hug from Shayla Young, 14, an eighth-grader.

The state dinner, only the fifth of this administration, was to feature violinist Itzhak Perlman as entertainment for the royal couple and dinner guests in the East Room.

"My sense is that there will be a lot of pleasant conversation," said Tony Snow, the White House press secretary. *