The $3.1 trillion budget President Bush sent to Congress yesterday promises to bring the federal deficit to near-record levels due to a $145 billion economic stimulus package and plunging corporate tax receipts. The budget deficit is expected to reach $410 billion in this fiscal year, just shy of the record set four years ago. The deficit for fiscal year 2009, which begins in October, is estimated at $407 billion.

Economists say that while these deficit projections are enormous, the reality is likely to be far more severe because the administration is assuming a rosy picture of economic growth that is unlikely to bear out. If growth is more sluggish, as the Federal Reserve, the Congressional Budget Office, and others predict, the deficit will balloon.

The budget, which is for the 2009 fiscal year, is a 6% increase from projected spending in this year’s $2.9 trillion budget. Highlights include making the Bush tax cuts permanent and cutting $196 billion from Medicare and Medicaid in the next five years. The budget was widely panned by Democrats, who said it underestimated the cost of repairing the alternative minimum tax and failed to set aside enough funding for the wars in Iraq and Afghanistan. Mr. Bush also fielded some criticism from his own party, including from the ranking Republican on the Senate Budget Committee, Senator Gregg of New Hampshire.

According to the administration’s estimates, the gross domestic product adjusted for inflation is expected to grow 2.7% this year and 3% in 2009. The Fed, meanwhile, is predicting growth to be as little as 1.8% this year and 2.3% in 2009.

If growth is one percentage point below estimates, that shortfall would tack on an additional $14 billion to the deficit this year, $46.3 billion next year, and a total of $705.5 billion overall for the next five years, according to the administration’s own estimates.

“The administration’s economic assumptions are clearly too optimistic,” an economist at the Brookings Institution, Douglas Elmendorf, said, adding that they are far higher than other estimates. The Blue Chip Consensus, which polls private businesses, found that GDP would grow by 2.2% this year, and 2.7% in 2009. Its five-year estimate is 2.7% for GDP growth. The CBO estimates 2008 GDP at 1.7%, 2009 GDP at 2.8%, and the five-year forecast is 2.8%.

“This all points to the fact that the deficit will be significantly larger than the administration projects,” Mr. Elmendorf said.

Late last year, the Fed began releasing its forecast for economic growth four times a year rather than twice, and it also began including expectations for growth three years out, which is widely considered its view of long-term GDP growth. In November, the last time it released its forecast, it estimated GDP growth to be as little as 2.5% in 2010. If the Fed is correct, it would mean a 0.4% dip in the administration’s estimates for growth, leading to an additional $280 billion for the deficit during the next five years.

“The unintended consequence of the Fed releasing more data is that we can now compare its long-term forecast with that of the administration,” said Vincent Reinhart, who was the director of the Fed’s Division of Monetary Affairs until October, when he joined the American Enterprise Institute as a resident scholar.

The budget faces other hurdles in addition to the risks of a ballooning deficit.

The budget includes $70 billion in funds for the wars in Iraq and Afghanistan, and would eliminate or cut down 151 programs that Mr. Bush said were unnecessary, including art education in the schools and mental health services. The budget also would eliminate a $283 million federal program to help make homes more energy efficient.

The Democrats said the budget provided no financing for the war after 2009, and also vastly underestimated the cost of fixing the alternative minimum tax.

“President Bush’s budget proposal is what we expected, but not what we need,” Rep. Charles Rangel said in a statement. “American families are desperately looking for leadership that will bring about change to address growing concerns with the economy, the lack of affordable health care and the continuing wars in Iraq and Afghanistan. Unfortunately, the Bush budget offers few changes from years past and little hope for strengthening opportunities for working families in the years to come.”

Mr. Bush also heard Republican criticism.

“Any budget, to be effective, needs to address the unsustainable growth of entitlement spending, which is the single biggest factor contributing to the long-term fiscal crisis we face,” Mr. Gregg said in a statement. “A budget also needs to honestly address the numbers contributing to its bottom line, such as fully funding the expected costs of the war on terror.”