Congress' investigative arm says fewer inspections of imported food and limited access to animal vaccines expose the U.S. food supply to tampering.

The Government Accountability Office (GAO) acknowledged food, health and security officials have taken steps to protect the nation's $1 trillion agriculture industry but said gaps in surveillance and response mechanisms remain, the Wall Street Journal said.

The agency's report singled out as particularly worrisome a decline in the number of the agricultural inspections at ports of entry, considered the first line of defense in blocking foreign plant and animal diseases.

In 2002, the number of inspections totaled 40.9 million, but these dropped to 37.5 million in 2004.

The GAO also warned a deliberate release of a plant or animal disease could result in widespread economic disruption, given the nation's $1 trillion agriculture industry accounts for 13% of gross domestic product and 18% of domestic employment.