It’s a port official’s worst nightmare: Cargo transported into the United States includes a smuggled nuclear “dirty bomb” that, when detonated, kills or injures hundreds and harms the U.S. economy by disrupting the flow of commerce into and out of the nation.

In recent years, Homeland Security officials have emphasized the need for a risk-based approach to cargo screening to prevent such a nightmare. “Risk-based” means that inspectors focus their attention on those cargo shipments that might pose the greatest potential threat of smuggling, terrorism or criminal activity. To date, that approach has served our nation well: providing a high level of security while also allowing for the free flow of goods into the United States through the international supply chain.

Despite this success, Congress passed a law last year mandating the 100-percent screening of all cargo shipments coming into the United States. Once you can get past the superficial appeal of the soundbite, a 100-percent regime is simply not the best approach. Not only is the security model complicated and expensive from a logistical perspective (based on the significant amount of technology and labor resources implementation would require), a growing body of research suggests it would actually make the nation less safe.

Rather than implementing such a restrictive mandate, Congress should consider collaborating with the private sector to find sensible alternatives for supply chain security.

This is precisely the point that Homeland Security Secretary Michael Chertoff made in a September 5 speech at the Brookings Institute in Washington, D.C., where he argued that the government should not try to “micromanage the business operations” of U.S. companies, but should look to partnerships between government and industry to protect the cargo shipment sector and our vital transportation infrastructure.

Secretary Chertoff has been working with these issues for more than three years, and he understands not only the difficulties inherent in a 100-percent scanning model, but also the opportunities inherent in a robust and constructive partnership between the public and private sectors.

The private sector, working closely with Homeland Security and port officials, has already developed strong protocols for risk-based cargo scanning that are paying dividends. This fact was noted in August 2008 report issued by the Government Accountability Office , Congress’s watchdog arm, that noted the tremendous progress in international cooperation on cargo security inspections.

This success has been driven by forward-thinking leaders in the private sector and the government who understand the need for balance in security and a free flow of commerce. Our focus should not be on attempting to identify, analyze and quantify the many unknowns about implementing a 100-percent approach. Instead, we should be strengthening industry-government partnership efforts to forge a new and sensible way forward on cargo security.

Asa Hutchinson is the Chairman of the Safe Commerce Coalition.