A ballooning US government budget deficit that could reach nine trillion dollars over a decade threatens to dent President Barack Obama's reform plans and thwart long term economic growth.

Forecasts by the White House and a congressional financial watchdog showed persistent large budget deficits even after the recession gripping the world's largest economy ends possibly this year.

The White House projected a whopping $9.05-trillion deficit for the 2010-2019 period, a $2-trillion increase from the February estimate made a month after Obama entered office and inherited a gaping deficit from his predecessor George W. Bush.

The Congressional Budget Office (CBO), the financial watchdog of Congress, meanwhile, offered a more optimistic projection — $7.13-trillion — assuming all Bush administration-imposed tax cuts expired in two years.

The White House, however, trimmed the 2009 fiscal budget deficit projection to $1.58-trillion from the previous estimate of $1.84-trillion.

Still, the deficit, stemming mostly from aid to the financial system and fiscal stimulus to jolt the economy from recession, represents more than 11 percent of gross domestic product (GDP), the largest as a share of the economy since World War II, analysts pointed out.

Under assumptions by both the White House and the CBO, the United States will consistently run up large deficits of around three to four percent of GDP.

"Permanent deficits of this size are a real negative for long-run economic growth, pushing up interest rates and reducing the amount of capital available for private investment, ultimately reducing productivity growth," warned Augustine Faucher, director of macroeconomics for Moody's Economy.com.

"And the problem will only get worse as baby boomers retire, requiring greater federal spending" on health care and social security, he said.

To close the deficit and boost long-run growth, he said, policymakers would need to raise taxes and cut spending, steps they have been unwilling to take.

The White House acknowledged the alarming fiscal situation but blamed the Bush administration for the mounting deficit.

"Overall, it underscores the dire fiscal situation that we inherited and the need for serious steps to put our nation back on a sustainable fiscal path," said the White House's Office of Management and Budget director Peter Orszag.

Administration officials argued that if the Bush administration had abided by budget guidelines, the projected 10-year deficit would be five trillion dollars smaller.

But Obama's Republican critics stepped up their calls for the president to abandon his key reform plans to remake US health care and combat climate change that some estimate could cost several trillions of dollars.

"It?s time for the administration and congressional Democrats to face the consequences of this dangerous fiscal agenda and change course," said John Boehner, Republican minority leader of the House of Representatives.

"The alarm bells on our nation?s fiscal condition have now become a siren," added Senate Republican leader Mitch McConnell.

But Orszag pointed out that seven months of Obama administration policies had already seen the estimated deficit for the 2009 fiscal year, which ends September 30, trimmed by $262-billion.

"We now expect that the policies put in place to repair the financial system are likely to cost taxpayers less than previously anticipated," he said.

The government has pumped hundreds of billions of dollars into the fragile financial system battered by a crisis stemming from a home mortgage meltdown that plunged the world's largest economy into recession.

The CBO, a nonpartisan statutory watchdog which plays a critical support role to lawmakers by providing cost estimates, also warned that large deficits and resulting increases in federal debt over time would reduce economic growth.

The total US public debt outstanding is currently at $11.6-trillion.

In its economic forecast, the White House projected that US gross domestic product (GDP) would shrink by 2.8 percent this year as it shakes off a prolonged recession, revising its previous forecast of a 1.2 percent decline.

It expected growth to turn a positive 2.0 percent in 2010, accelerate a year later to 3.8 percent and exceed 4.0 percent per year in the 2012-2014 period.

The Obama administration and the CBO also warned of continuing job layoffs even as recovery seems imminent, expecting the unemployment rate to peak above 10.0 percent next year.