WASHINGTON (Reuters) - More funding is needed to address a growing "infrastructure deficit" in the United States, as aging bridges, roads and highways crumble, putting drivers at risk, the U.S. Department of Transportation said in a report on Friday.

In the report to Congress, the agency said all levels of the U.S. government would need to spend between $123.7 billion and $145.9 billion per year to maintain and improve the condition of roads and bridges alone.

In 2010, the latest year for which figures are available, about $100 billion was spent, including almost $12 billion in funds provided by American Recovery and Reinvestment Act, the stimulus package crafted to pump money into the economy during the severe recession.

The preventative maintenance backlog for transit reached $86 billion and was expanding at about $2.5 billion per year, according to the report. The shortfall affects individual commuters as well freight movement around the country.

Over two-thirds of the 604,493 bridges in the United States were 26 years old or older as of 2010.

Of the total bridges, 11.5 percent were structurally deficient, while 12.8 percent were functionally obsolete, it said, meaning they did not meet current design standards.

Spending on public transit systems including rail and buses was also falling behind.

The report indicated that as much as $24.5 billion was needed per year to improve the condition of transit rail and bus systems. In 2010, total spending was $16.5 billion.

Some transit systems were running rail cars more than 30 years old, but the report found that over 75 percent of needed repairs affected other facets of transit systems, such as rail stations, trestles, and power substations.

The department's "conditions and performance" report, given to Congress every two years, came days after U.S. President Barack Obama announced a four-year, $302 billion plan to repair the country's crumbling roads and bridges.

The proposal, which relies on tax reform for funding, was not expected to gain traction on Capitol Hill.

Congress faces a September 30 deadline to renew federal funding for transportation programs and the Highway Trust Fund that helps pay for road and bridge projects on the verge of insolvency.

(Reporting by Ros Krasny; Editing by Jeffrey Benkoe)