More cocaine is likely to come into the United States from South America as the U.S. diverts resources from its drug-control strategy to hurricane relief and the War on Terror, congressional investigators say.

The report prepared by the Government Accountability Office, an investigative arm of Congress, found that U.S. cocaine seizures from 2000 to 2004 increased by 68 percent to a record 196 metric tons in the "transit zone," the area between the U.S. and South America.

But the Pentagon's attention to armed conflicts in Afghanistan and Iraq and the Homeland Security Department's focus on Hurricane Katrina threaten to undermine recent achievements, the GAO said in its report.

The report, an advance copy of which was obtained by The Associated Press, offers a sobering look at the future of government efforts to stymie America's $65 billion illegal drug habit. It notes that while drug seizures have increased, U.S. cocaine supplies and the number of users (2 million) have not fallen, apparently due to a rise in shipments.

"We need to be more effective and better prepared because these are routes that not only move illicit drugs today, but can easily move other more dangerous commodities such as terrorists in the future," said Sen. Charles Grassley, R-Iowa, who requested the study.

In the report, the GAO pointed in particular to reduced use of the Navy's P-3 maritime patrol aircraft "due to structural problems," a slowing Coast Guard response because of aging ships, and a surface radar system on Coast Guard aircraft that is "often inoperable."

Since fiscal year 2000, the number of hours flown by the Navy P-3s has decreased nearly 60 percent to about 1,500 hours in fiscal year 2005, according to the study.

"Various factors pose challenges to maintaining the current level of transit zone interdiction operations," the GAO said in calling on the Pentagon and Homeland Security to develop a long-term strategy to plan for a likely shortfall in ships and aircraft.

In their official responses, the departments said they were working to boost resources for drug control but acknowledged they were constrained partly by the perceived threat level as well as availability of funding.

The decline in Navy aircraft for drug patrols should not be interpreted as "a lack of DoD resolve," the Pentagon wrote, citing "war-fighting requirements."

While committed to "robust support" of drug control, "unforeseen events such as Hurricane Katrina relief efforts may temporarily impact asset availability," Homeland Security said in its response.

The GAO attributed recent successes in drug seizures to better intelligence and increased cooperation between the Homeland Security, Defense and Justice departments, allowing them to succeed with fewer resources based on targeted raids.

It also cited the use of Coast Guard helicopters equipped with machine guns and sniper rifles to hunt down drug boats, as well as cooperation from several allied nations — France, Netherlands and the United Kingdom — that helped make up for the dropoff in Pentagon aircraft for surveillance.

Still, the decline in U.S. antidrug activity poses challenges, the report said.

Cooperating nations in South America have said they don't have the resources to compensate for declining U.S. involvement, the report said, citing a lack of secure communication equipment or vessels of their own.

"While some short-term fixes have been taken, the longer-term implications of further declines in the availability of monitoring and interdiction assets have not been addressed," the GAO said.