WASHINGTON — President Obama is putting the finishing touches on an ambitious first budget that seeks to cut the federal deficit in half over the next four years, primarily by raising taxes on business and the wealthy and by slashing spending on the wars in Iraq and Afghanistan, administration officials said.

In addition to tackling a deficit swollen by the $787 billion stimulus package and other efforts to ease the nation's economic crisis, the budget blueprint will press aggressively for progress on the domestic agenda Obama outlined during the presidential campaign. This would include key changes to environmental policies and a major expansion of health coverage that Obama hopes to enact later this year.

A summary of Obama's budget request for the fiscal year that begins in October will be delivered to Congress on Thursday, with the complete, multi-hundred-page document to follow in April.

In his weekly radio and Internet address yesterday, he expressed determination to "get exploding deficits under control" and described his budget request as "sober in its assessments, honest in its accounting, and lays out in detail my strategy for investing in what we need, cutting what we don't, and restoring fiscal discipline."

Reducing the deficit, he said, is critical to the nation's future: "We can't generate sustained growth without getting our deficits under control."

Obama faces the long-term challenge of retirement and health programs that threaten to bankrupt the government years down the road, as well as the more immediate problem of deficits bloated by spending on the economy and financial-system bailouts. His budget proposal takes aim at the short-term problem, administration officials said, but also would begin to address the nation's chronic budget imbalance by squeezing savings from the federal health programs for the elderly and the poor.

Even before Congress approved the stimulus package earlier this month, this year's deficit was projected by congressional budget analysts to approach $1.2 trillion, or 8.3 percent of the overall economy, the highest since World War II. With the stimulus and other expenses, some analysts say the annual gap between federal spending and income could approach $2 trillion when the fiscal year ends in September.

DRAMATIC REDUCTION

Obama proposes to dramatically reduce those numbers by the end of his first term, cutting the deficit he inherited in half, said administration officials, speaking on condition of anonymity because the budget has yet to be released.

His budget plan would keep the deficit hovering near $1 trillion in 2010 and 2011, but shows it dropping to $533 billion in 2013 — still high in dollar terms, but a more manageable 3 percent of the overall economy.

To get there, Obama proposes to cut spending and raise taxes. The savings would come primarily from "winding down the war" in Iraq, a senior administration official said. The budget assumes that the nation will continue to spend money on "overseas military contingency operations" throughout Obama's presidency, the official said, but that number is significantly lower than the nearly $190 billion the nation budgeted for Iraq and Afghanistan last year.

Obama also seeks to increase tax collections, primarily by making good on his promise to eliminate the temporary tax cuts enacted in 2001 and 2003 for wealthy taxpayers, whom Obama defined during the campaign as those earning more than $250,000 a year. Those tax breaks would be permitted to expire on schedule for the 2011 tax year, when the top tax rate would rise from 35 percent to more than 39 percent.

Obama also proposes to maintain the tax on estates worth more than $3.5 million, instead of letting it expire next year. And he proposes "a fairly aggressive effort on tax enforcement" that would target tax havens and corporate loopholes, among other provisions, the official said.

Overall, tax collections under the plan would rise from about 16 percent of the economy this year to 19 percent in 2013, while federal spending would drop from about 26 percent of the economy, another post-war high, to 22 percent.

The budget also puts in place the building blocks of what administration officials say will be a broad restructuring of the U.S. health system.