* Pelosi urges mid-Feb action on stimulus
* Economists warn of worsening unemployment
* Obama expects price tag at "high end" of estimates
By John Crawley and Lisa Lambert
WASHINGTON, Jan 7 (Reuters) - Congress must approve a sweeping economic stimulus package by mid-February or the United States will face a deepening crisis and more job losses, House Speaker Nancy Pelosi said on Wednesday.
Democrats had hoped to present President-elect Barack Obama with a recovery plan on Jan. 20, his first day in office, but the informal target has now slipped by at least a month as the political realities begin to take hold.
At a Democratic-sponsored forum on suggested approaches for a recovery plan, Pelosi said lawmakers must ensure any response has a rapid and meaningful impact on the reeling economy.
"We need action," Pelosi said. "Failure to act quickly will only lead to more job losses and more economic pain for America."
Democrats have talked about spending about $775 billion over two years to invest in public works projects, expand aid to cash-starved state governments and give more help to the poor and unemployed who have been hit hard by the yearlong recession.
Obama plans to propose $310 billion in tax cuts for the middle class and businesses as part of the package.
Some U.S. governors and economists are pushing for a larger package of around $1 trillion. Many Republicans want a more modest bill, possibly in the range of $500 billion.
Obama said Wednesday he was still talking to congressional leaders about the plan.
"We expect that it will be on the high end of our estimates but will not be as high as some economists have recommended because of the constraints and concerns we have about the existing deficit," Obama told a news conference.
Democrats said the stimulus bill would include measures to strengthen high-tech infrastructure, promote cleaner energy, rebuild bridges and modernize schools.
"This is not your grandfather's public works bill," Pelosi said, referring to job-creation programs during the Great Depression of the 1930s.
Leading economists at the forum agreed that action was needed quickly.
Former Labor Secretary Robert Reich, an Obama transition adviser, said the United States would lose another 3 million jobs this year if a stimulus package is not approved soon.
"Unemployment will rise to 10 percent of the work force by the end of this year, and underemployment -- including people working part-time who would rather be working full time, and those too discouraged even to look for work -- will reach 15 percent," said Reich, who served under former President Bill Clinton.
The U.S. Bureau of Labor Statistics will release its December jobs report on Friday and economists expect the unemployment rate to rise to 7.0 percent from 6.7 percent in November, which was the highest since 1993. The U.S. has lost 2 million jobs during the recession, which was brought on by the bursting of a credit and housing bubble.
"The financial system is broken," Mark Zandi, chief economist at Moody's Economy.com told lawmakers. He said that he supported a stimulus bill of $750 billion to $800 billion.
"The Federal Reserve is just not up to the task of getting the economy going."
Reich said Congress should not be wary of borrowing to pay for a stimulus, pointing out that U.S. debt at the end of the World War Two was more than 100 percent of gross domestic product.
Public debt is currently around 40 percent of GDP. (Additional reporting by Kevin Drawbaugh and Richard Cowan, editing by Tom Hals)