In his weekly radio and Internet address, Mr. Obama sought to inject a positive note into the economic outlook by releasing a report from his advisers that estimated the number of jobs that could be created with his plan by the end of 2010.

The report noted, however, that at least five million jobs, and probably many more, will have been lost during the downturn. So even if the most optimistic projections bear out, unemployment in December 2010 will still be higher than it was in December 2007.

Mr. Obama’s address was his latest effort to sell a $775 billion proposal to Congress, whose leaders have pledged to adopt a bill by mid-February, and to Americans stung by the recession.

“The jobs we create will be in businesses large and small across a wide range of industries,” Mr. Obama said. “And they’ll be the kind of jobs that don’t just put people to work in the short term, but position our economy to lead the world in the long term.”

Without an economic recovery plan, the report warned, the unemployment rate could hit 9 percent, up from 7.2 percent now. If the plan is adopted, unemployment is still expected to rise but then fall late this year.

The report, and Mr. Obama’s speech, also seemed intended to counter criticism, particularly from some Republicans, that his plan would create bureaucracies rather than put people to work.

The 14-page report, prepared by Christina D. Romer, who is Mr. Obama’s selection to lead his Council of Economic Advisers, and Jared Bernstein, an economic adviser to Vice President-elect Joseph R. Biden Jr., provides specific examples for the first time of the types of jobs that could be created, including a detailed, industry-by-industry breakdown.

Mr. Obama said his plan could create about 500,000 jobs by making new investments in clean energy, doubling the production of alternative energy over three years and improving the energy efficiency of government buildings and homes.

He said building solar panels and wind turbines and developing fuel-efficient cars would create “made-in-America jobs” that could not be outsourced.

The report also suggested that nearly 400,000 jobs could be created by building and repairing roads, schools and bridges. More than 200,000 jobs could be created in health care, particularly by creating a nationwide system of computerized medical records.

Some conservatives argue that jobs that exist only as a result of temporary government spending should not be viewed as providing real, long-term growth. On Capitol Hill, lawmakers are engaged in vigorous debate over how best to stimulate the economy and to create jobs. Some Democrats say Mr. Obama’s plan would be more effective if it were to focus fewer dollars on tax cuts and more on government spending, especially in the energy sector.

Some top Republicans, meanwhile, are pushing for even broader tax cuts. “We want to make sure it’s not just a trillion-dollar spending bill,” said the Republican leader, Senator Mitch McConnell of Kentucky, “but something that actually can reach the goal that he has suggested.”

Obama transition officials have said that the president-elect’s proposed middle-class tax cut — called “Making Work Pay,” which would provide $500 for individuals and $1,000 for couples by reducing payroll tax withholdings — is “nonnegotiable.” Mr. McConnell is pushing an alternative that would cut the tax rate for most middle-income workers, to 15 percent from 25 percent.

In the campaign, Mr. Obama vowed to create one million jobs, and after winning election he put forth a plan to create up to three million. The report now puts the figure at roughly 3.7 million, the midpoint of an estimated range of 3.3 million to 4.1 million jobs by the end of next year. Even now, though, it is merely an estimate based on a model that assumes a million jobs for stimulus spending equal to 1 percent of the nation’s economic output.

In the report, Mr. Obama seems to address the criticism from some Democrats that his economic stimulus plan favors tax cuts over creating new jobs. The report concedes that tax cuts and giving aid to states “are likely to create fewer jobs” but says the tax cuts are needed to jump-start the economy quickly.

“There is a limit,” the report said, “on how much government investment can be carried out efficiently in a short time frame.”