WASHINGTON  President-elect Barack Obama signaled on Saturday that he would pursue a far more ambitious plan of spending and tax cuts than anything he outlined on the campaign trail, setting the tone for a recovery effort that could absorb and define much of his term.

In the Democrats’ weekly radio address, Mr. Obama said he would direct his economic team to craft a two-year stimulus plan with the goal of saving or creating 2.5 million jobs. He said it would be “a plan big enough to meet the challenges we face.”

Mr. Obama said he hoped to sign the stimulus package into law soon after taking office on Jan. 20. He is already coordinating efforts with Democratic leaders in Congress, who have said they will begin work next month.

Advisers to Mr. Obama say they want to use the economic crisis as an opportunity to act on many of the issues he emphasized in his campaign, including cutting taxes for lower- and middle-class workers, addressing neglected public infrastructure projects like roads and schools, and creating “green jobs” through business incentives for energy alternatives and environmentally friendly technologies.