U.S. president-elect Barack Obama recalled the spirit of America's forefathers Saturday during a historic, six-city train trip that followed the same route Abraham Lincoln travelled nearly 150 years ago.

The journey culminated in Washington D.C. around 7 p.m., kicking off three days of festivities in advance of Obama's inauguration on Tuesday, Jan 20.

Earlier in the day, Obama gave an emotional speech in Baltimore, Md., calling on citizens to forge a "new declaration" of independence and to live up to the hopes and dreams of the country's founders.

"We are here today not simply to pay tribute to those patrons who founded our nation in Philadelphia, or defended it in Baltimore, but to take up the cause for which they gave so much," said Obama, speaking to about 35,000 people who crammed into the Baltimore's central square.

"The trials we face are very different today, but they are severe in their own right," said Obama, referring to global economic woes, two wars and climate change.

"Only a handful of times in our history has a generation been confronted with challenges so vast."

Fittingly, Obama referred to the Battle of Baltimore, which was a turning point in the War of 1812 in which the American forces beat back a massive British sea invasion during a night of heavy fighting.

"And when that night was over, they raised the flag in triumph," Obama said, adding that the American victory in Baltimore inspired poet Francis Scott Key to write "The Star Spangled Banner."

Obama's Baltimore speech came part-way through a six-city whistle-stop that tour follows the same route Abraham Lincoln travelled nearly 150 years ago.

"We began this train trip in Philadelphia earlier today and it is fitting that we did so, because it was there that our American journey began," said Obama.

Biden's city

Earlier in the day, the "Obama Express" rolled through Wilmington, Del., the home of vice president-elect Joe Biden, who joined him in front of thousands of people.

"Delaware, I'm asking Joe Biden to take one more trip to Washington," said Obama, referring to Biden's daily commute by train to the capitol that earned him the nickname "Amtrak Joe."

"Together, we know that there's work to be done," Obama continued. "Together we know that America faces its own crossroads: a nation at war; an economy in turmoil; an American dream that feels like it's slipping away. Together we know that the American people are facing adversity, and the time has come to pick ourselves up once again."

The train will also slow down in the towns of Claymount, Del., and Edgewood, Md., so residents can wave to Obama, who will be perched on the train's back balcony.

Crowds are expected to gather on highway overpasses, in parking lots and at train stations to cheer on Obama, his daughters and Michelle, who celebrates her 45th birthday today.

Obama, his wife Michelle, and their two daughters Malia and Sasha, began their train trip Saturday morning in Philadelphia's historic 30th Street train station, with temperatures well below freezing.

Before beginning the 220-kilometre trip, the president-elect delivered a short speech in the station's grand terminal, saying it was fitting that he would begin his journey to Washington in the city where "our American journey began."

Obama likened his nation's current struggle with a depressed economy, global warming and a two-front war on terror to the founding fathers' early struggle to establish a new republic.

"And yet while our problems may be new, what is required to overcome them is not," Obama said. "What is required is the same perseverance and idealism that our founders displayed. What is required is a new declaration of independence, not just in our nation, but in our own lives -- independence from ideology and small thinking, independence from prejudice and bigotry, independence from selfishness."

'Our future is our choice'

In his speech, Obama warned that overcoming the current challenges would not be easy, and asked for Americans' patience as he begins his work in the White House.

But he told Americans that they, too, can work for change.

"I believed that our future is our choice," Obama said. "And that if we could just recognize ourselves in one another and bring everyone together -- Democrats, Republicans, independents, north, south, east, west, black, white, Latino, Asian, Native American, gay and straight, and disabled and not -- then not only would we restore hope and opportunity in places that yearn for both but maybe, just maybe, we might perfect our union in the process."

The 80-year-old train, a Georgia 300, is the same one Obama took as he travelled through Pennsylvania for last April's primary.

The train trip follows the latest of Obama's weekly radio addresses, in which the president-elect looked forward to his inauguration as "a celebration of the American people."

While he warned of "difficult days" ahead, Obama recalled the inauguration speech delivered by George Washington.

"Addressing the nation that day, Washington explained his decision to serve, saying, 'I was called by my country, whose voice I can never hear but with veneration and love.' This Tuesday, we can reaffirm our own veneration and love for our country and our democracy," Obama said. "We can once again provide an example to the world, and move forward with a renewed sense of purpose and progress at home."

With files from The Associated Press