WASHINGTON — Two days from the White House, President-elect Barack Obama joined a vast throng yesterday at a joyous pre-inauguration celebration staged among marble monuments to past heroes. "Anything is possible in America," declared the man who will confront economic crisis and two wars when he takes office.

"Despite the enormity of the task that lies ahead, I stand here today as hopeful as ever that the United States of America will endure — that it will prevail, that the dream of our founders will live on in our time," the president-elect said at the conclusion of a musical extravaganza that featured U2, Beyonce, Bruce Springsteen and a host of other stars.

Obama assured an anxious nation that "we will overcome what ails us now" with a faltering economy and two wars abroad.

Obama and his family held the seats of honor at the event, and a crowd of hundreds of thousands spilled from the base of the Lincoln Memorial toward the Washington Monument several blocks away in the cold, gray mid-January afternoon.

It was the high point of a full day of pre-inaugural events that included a wreath-laying at the Tomb of the Unknowns at Arlington National Cemetery and a morning church service where children recalled the life of civil rights leader Martin Luther King Jr.

Obama's motorcade drew ever-larger crowds as the day wore on and he and his wife, Michelle, and their children, Sasha and Malia, crisscrossed the city.

"Just another typical Sunday," deadpanned the Rev. Derrick Harkins, pastor at the Nineteenth Street Baptist Church, where the soon-to-be first family prayed.

Of course it was anything but — a run-up, in fact, to the first inauguration of an African-American president in a nation founded by slave owners.

Obama's aides said he was readying an inaugural address that would stress twin themes of responsibility and accountability, and they predicted he would devote his first week in office to economic recovery, setting in motion a 16-month troop withdrawal from Iraq and decreeing a code of ethics for his administration.

With the economy weak and growing weaker, banks in trouble and joblessness rising, Obama's team was careful to warn against any expectation that he would be a miracle worker.

"I think it's fair to say that it's going to take not months but years to really turn this around," said David Axelrod, a political strategist expected to have White House space mere paces from the Oval Office.

Obama said as much in his own brief remarks.

"I won't pretend that meeting any one of these challenges will be easy. It will take more than a month or a year, and it will likely take many," he said.

He stood alone at the base of the steps before the statue of a seated Lincoln looking out at a crowd every bit as large as the one King addressed a generation earlier in his "I have a dream" speech that was a defining moment of the civil rights era.

MORE TO COME

An even larger audience is forecast for the inauguration outside the Capitol tomorrow, with estimates running into the millions. Agencies in charge of logistics and security said they would enforce a ban on personal auto traffic across the Potomac River bridges from Virginia into Washington and seal off a large portion of the downtown area. Access to buildings along the inaugural parade route down Pennsylvania Avenue was limited to those who gained Secret Service approval in advance.

Obama's day began at the Tomb of the Unknowns at Arlington National Cemetery, where he and Vice President-elect Joseph Biden laid a wreath in memory of fallen heroes. The two men placed their hands over their hearts as a uniformed bugler played taps in a somber opening to a festive day.

The scene was quite different at the church a few miles away, where the congregation erupted in applause when Obama and his family walked to their seats.

"Understand that God has prepared you, and God has placed you, and God will not forsake you," Harkins told the incoming president.

Children sang and spoke selected readings that recalled King, killed in 1968.

"Martin Luther King walked so that Barack Obama could run," said one boy. "Barack Obama ran so that all children could fly," added another, standing a few feet away from Obama.

At the Lincoln Memorial a few hours later, King's son, Martin Luther King III, had a brief speaking role.

For the most part, the program was a festival of music, the songs chosen to make their points. Mary J. Blige sang, "Lean on Me," Springsteen performed "The Rising," and Obama mouthed the words as 89-year-old Pete Seeger pitched in with "This Land is Your Land."

Many in the crowd sang along with Beyonce's soulful finale, "America the Beautiful."

In film clips at earlier moments, Obama was cast as heir to Franklin Delano Roosevelt, John F. Kennedy and even Lincoln, who the president-elect said was "the man who in so many ways made this day possible."

FOCUS ON ECONOMY

As Obama moved around town in a pre-inaugural motorcade, his aides blanketed Sunday's interview programs.

With the nation facing the most difficult economic crisis since the Great Depression, they all agreed that recovery was the principal challenge facing the new president.

"What's important ... is ensuring that those that have had the short end of the stick for the last few years — make sure that they get the help that they need, that this administration begins to create the jobs and give some financial stability to families so that they can feel hopeful about going forward," said Robert Gibbs, who will serve as Obama's White House press secretary.

"Three million, 4 million jobs is going to make a very big difference," said Lawrence Summers, a top economic adviser to the incoming president, referring to the goal Obama has set. "It all depends on psychology, but we are going to be leaning forward throughout this administration. The president's made it clear that our errors are not going to be of standing back."

The Democratic-controlled Congress has already made a quick start on the president's recovery program, clearing the way for use of the second $350 billion for the financial industry bailout created last fall, and launching an $825 billion stimulus measure. Democratic leaders have pledged to have the legislation ready for Obama's signature by mid-February.

House Speaker Nancy Pelosi, D-Calif., also endorsed Obama's call for a summit meeting to begin controlling spending on huge government benefit programs such as Social Security, Medicare and Medicaid. She said even benefit cuts should be included as an option for discussion.

"You put everything on the table. The only thing we didn't want to put on the table is eliminating" the programs, she added.

The Senate appears ready to confirm several of Obama's Cabinet appointees as soon as he signs the nomination paperwork tomorrow, although not everything has been smooth for Obama and his transition team.

Treasury Secretary-designate Timothy Geithner's confirmation has been delayed for at least a few days because of his disclosure that he had failed to pay some federal taxes earlier in the decade. Bill Richardson withdrew as Obama's commerce secretary choice because of a grand jury investigation in New Mexico, where he is governor.