Gen. John Kelly, head of U.S. Southern Command, said that U.S. forces seized 150 to 200 tons of cocaine during operations on the high seas last year. But he told the Senate Armed Services Committee that if the budget cuts stand, "Next year all of that will make its way ashore and into the United States."

With the U.S. at war in Afghanistan, other military commanders around the world have struggled to get intelligence, surveillance and other assets in their regions. Kelly acknowledged that he doesn't get too much down at Southern Command, but he'd get "just about zero" if the automatic budget cuts continue.

Both Navy and Coast Guard ships are used to patrol the waters of the Caribbean and the eastern Pacific, but Navy officials have already announced that the deployment of the frigate USS Thach may be cut short and a second frigate, the USS Rentz, may not be sent out.

Critics have questioned the Pentagon's actions, saying that defense officials have been overstating the ramifications of the cuts. Pentagon officials, meanwhile, say that across-the-board cuts give them little flexibility in how they apply the savings.

The Pentagon was already facing a $487 billion, 10-year reduction in projected spending as part of the budget law that Obama and congressional Republicans agreed to in August 2011. In addition to that, the military is grappling with $43 billion in across-the-board cuts that went into effect on March 1.

Kelly said the cuts would hamper his efforts to meet the president's goal of intercepting 40 percent of the illicit drug shipments flowing into the region by 2015. He said the ships are key to the fight, because the fast boats and other vessels used by smugglers can carry so much more drugs than they can transport by plane.

"The product that's flown out of primarily Venezuela by small aircraft ... might carry a ton, sometimes less than that, but roughly a ton," Kelly said during the hearing. "The profits are so lucrative they land and then they take the drug off the airplane, they just burn the airplane. So it's not even worth making the return trip to them, the profits are so high."

Meanwhile, some of the ships smuggling drugs, he said, can carry 10 to 20 tons of cocaine.

He said that with surveillance technology, U.S. military and law enforcement forces can identify drug traffickers more easily on the open seas and can often gain information about the drug networks from those they capture.

Kelly said the top three areas of cocaine production are Peru, Bolivia and Colombia, and as much as 20 percent of the cocaine moving through South America ends up in the United States. Large amounts also travel across the ocean into Africa, providing funding for insurgents and drug traffickers, and then on up into Europe.

Noting the Navy has also said that the deployment of the USNS Comfort hospital ship to South America will likely be either delayed or cut, Kelly said that some leaders in South America are beginning to question the United States' commitment to the region.

"The concern on the part of many of our Latin American friends and partners is that we're withdrawing," said Kelly. And he said that may open the door for more involvement by countries such as China and Iran, who are getting more active in investing and building in a number of South American nations.