WASHINGTON, Aug 3 (Reuters) US politicians treated the collapse of a highway bridge that killed or injured dozens of people as a jarring wake-up call to fix the nation's aging roads and bridges, but experts have been sounding the alarm for years with limited success.

Governors in at least four states -- Illinois, Minnesota, Iowa and Pennsylvania -- ordered new bridge inspections or were considering them following the collapse of the highway bridge over the Mississippi River in Minneapolis on Wednesday.

Other governors ordered administrative reviews, while federal lawmakers demanded action.

''A bridge in America just shouldn't fall down,'' said Sen.

Amy Klobuchar, a Minnesota Democrat at a news conference yesterday in Minneapolis. ''We have to get to the bottom of this.'' ''We should look at this tragedy that occurred as a wake-up call for us,'' said Senate Majority Leader Harry Reid, a Nevada Democrat. ''We have all over the country a crumbling infrastructure; highways, bridges and dams. We really need to take a hard look at this.'' Rep James Oberstar, the Minnesota Democrat who chairs the House Transportation and Infrastructure Committee, blamed President George W. Bush's administration for shortchanging road and bridge repair in a highway funding bill two years ago.

Bush, he said, ''failed to support a robust investment in surface transportation,'' adding the president insisted on only 2 billion dollar a year for bridge reconstruction when lawmakers were pushing for 3 billion dollar a year.

When Congress next rewrites the highway funding bill in 2009, ''we're not going to settle for a bargain-basement transportation'' policy, Oberstar said.

The problem of aging infrastructure is not new. A 2002 report by the Department of Transportation said about 30 per cent of the nation's highway bridges were structurally or functionally deficient.

While the report found the figure had been declining, it warned that all the country's bridges were deteriorating with age and growing traffic volumes were increasing the strain on them.

ALMOST FAILING 'D' GRADE A 2005 report by the American Society of Civil Engineers gave the country's infrastructure an unacceptable D grade -- almost failing. The group estimated the United States needed to spend 1.6 trillion dollar over five years to put its infrastructure into good shape.

''This has been out there for quite some time,'' said Kent Harries, an engineering professor at the University of Pittsburgh.

''It's not only the transportation and bridge infrastructure, it is infrastructure in general.'' Bridges actually received comparatively high marks in the civil engineering report: an acceptable C grade, compared with D notes for the country's aviation system, dams, drinking water, electric power grid and hazardous waste system.

Robert Dodds, head of the engineering department at the University of Illinois at Urbana-Champaign, said what made the bridge collapse so shocking was the general reliability of bridges nationwide.

''We take their safety for granted every day,'' he said.

But Harries said infrastructure failures happen more frequently than most people notice, pointing to the collapse of a concrete bridge box girder near Pittsburgh in 2005 and the recent explosion of a steam pipe in Manhattan. Part of the problem is finding maintenance funds.

''We recognize that there is a problem but there just seems to be this inability to move on it, partially I suspect because the problem is so amazingly large. The dollar values that we're talking about, they defy understand,'' Harries said.

Funding it all would require trillions of dollars. The only way to address the issue is to prioritize, he said, but then politics comes into play.

''The fact of the matter is nobody gets their name on a bridge repair,'' Harries said. ''You build a bridge, you get your name on it.'' REUTERS SAM BST0551