UPDATE 1-US three-month budget gap exceeds FY 2008 full year

WASHINGTON Jan 13 (Reuters) - The United States racked up a record $485 billion deficit for the first three months of fiscal 2009, exceeding the $455 billion gap for all of the previous year, the U.S. Treasury said on Tuesday.

In December, the government posted a deficit of $83.62 billion versus a year-ago surplus of $48.26 billion -- a wide swing that the Treasury attributed to a steep drop in corporate tax receipts and outlays from its financial rescue fund.

The December budget gap was in line with consensus forecasts of an $83 billion deficit from economists polled by Reuters.

The combined October, November and December deficit was nearly five times the year-ago budget hole of $107 billion, according to Treasury data.

The ballooning deficit could constrain President-elect Barack Obama's ability to revive the U.S. economy with a massive fiscal spending program this year. The deficit for fiscal 2009, which started Oct. 1, is expected to hit a staggering $1.186 trillion, according to the non-partisan Congressional Budget Office. This is even before an estimated $800 billion in proposed tax cuts and stimulus spending from Obama.

The December U.S. budget outlays rose to a $321.44 billion, a record for that month, from $228.72 billion in Dec 2007. The outlays included about $55 billion in spending from the Treasury's $700 billion financial rescue fund, known as the Troubled Asset Relief Program.

The Treasury also bought $21.2 billion worth of mortgage-backed securities from housing finance agencies Fannie Mae FNM.P and Freddie Mac FRE.P in December, bringing its investments in these securities to $66.47 billion in the year to date.

The $485 billion budget deficit more than quadrupled the year-ago

U.S. budget outlays through the first three months of fiscal 2009 topped $1 trillion for the first time ever, rising nearly $300 billion from the year-ago period.

Receipts, however, for the first three months sank by nearly 10 percent to $547.44 billion from $606.21 billion. Both individual and corporate income taxes fell for the period as the recessionary economy sapped earnings. (Reporting by David Lawder, Editing by Chizu Nomiyama)