* Obama urges cooperation, pledges swift action
* Transition team working on addressing economic crisis
* Bush warns Obama of challenges ahead
By Deborah Charles
CHICAGO, Nov 8 (Reuters) - Barack Obama said on Saturday that, with the long U.S. presidential election campaign over, now was the time for Americans to put aside political differences and work together to solve the economic crisis.
Obama, a Democrat who won a decisive victory against Republican John McCain in Tuesday's election to become the first black U.S. president as of Jan. 20, vowed to seek unity.
He noted Republican President George W. Bush and first lady Laura Bush had invited Obama and his wife Michelle to the White House on Monday and that the Bushes had offered to do all they could to help with Obama's transition.
"This speaks to a fundamental recognition that here in America we can compete vigorously in elections and challenge each other's ideas, yet come together in service of a common purpose once the voting is done," Obama said in the Democratic Party's weekly radio address.
"And that is particularly important at a moment when we face the most serious challenges of our lifetime," said Obama, who regularly attacked the Bush administration during the campaign for causing the now-global economic crisis.
Obama noted that figures released on Friday showed a 10th straight month of job losses, bringing the total number of unemployed Americans to about 10 million.
"Tens of millions of families are struggling to figure out how to pay the bills and stay in their homes," Obama said. "Their stories are an urgent reminder that we are facing the greatest economic challenge of our lifetime and we must act swiftly to resolve them."
'CAN'T AFFORD TO WAIT'
Obama said he and his transition advisory board -- a well-regarded group of business leaders, former top Washington officials and economic experts -- discussed the challenges at a meeting on Friday and started developing a series of policies to address the crisis.
"While we must recognize that we only have one president at a time and that President Bush is the leader of our government, I want to ensure that we hit the ground running on January 20th because we don't have a moment to lose," said Obama.
In his own weekly radio address, Bush congratulated Obama on his historic victory.
"No matter how we cast our ballots, all Americans have reason to be proud of our democracy. Our citizens have chosen a president who represents a triumph of the American story -- a testament to hard work, optimism and faith in the enduring promise of our nation," Bush said.
But he warned of the difficulties awaiting the president-elect.
"Our country faces economic challenges that will not pause to let a new president settle in," Bush said.
"This will also be America's first wartime presidential transition in four decades," Bush added. "We're in a struggle against violent extremists determined to attack us -- and they would like nothing more than to exploit this period of change to harm the American people."
Bush said his administration would work hard to ensure that that Obama and his team can "hit the ground running."
Obama vowed to help working class families and to stem the problems before they get worse.
He said the United States "can't afford to wait" to move forward with his priorities like clean energy, health care reform, improvements to the education system and tax relief for the middle class.
"I do not underestimate the enormity of the task that lies ahead," said Obama.
"We've taken some major actions to date, and we will need further actions during this transition and subsequent months," he said.
"Some of those choices will be difficult, but America is a strong and resilient country. I know that we will succeed if we put aside partisanship and work together as one nation. And that is what I intend to do." (Editing by John O'Callaghan)