The bow of the USS Thach was slicing the Pacific waters off Colombia's coast when the alarm suddenly blared across the US Navy frigate. It was time to hunt down a cocaine ship.

Armed sailors rushed to positions on the bridge and US Coast Guard personnel jumped on an inflatable boat to chase the drug smuggling vessel. After eight days at sea, the 240 sailors finally had a potential big catch.

The USS Thach was sailing the Pacific as part of Operation Martillo, a mission launched in January 2012 by the United States with Central American nations in an unprecedented militarization of the war on drugs.

Sometimes the smugglers try to outsmart the patrols by using fishing vessels or high-powered speed boats, but the most daring travel in makeshift semi-submersibles. Some can carry as much as a ton of drugs.

"We go on board these vessels and we try to determine whether or not they have contraband," said Lieutenant Eric Watkins, head of the ship's Coast Guard crew.

"We make sure we have 100 percent accountability of all the space on board and that is basically how we find drugs."

This time, surveillance airplanes detected a suspect ship in international waters, but the smugglers tossed their cargo into the ocean and no arrests were made. The Coast Guard crew fished out 70 brown packages, each containing one kilogram (2.2 pounds) of cocaine.

The sailors spend long days at sea without seeing much action. They fill their time by conducting rescue exercises, testing light weapons or doing chores like re-painting the bridge.

But when the "phase 1" alarm sounds, the crew is on a war footing in less than 30 minutes.

"Eighty percent of the narcotics that are ultimately destined for the United States transit through these waterways, so it makes sense for us to have a very substantial presence down here," said USS Thach's blond and broad-shouldered Captain Hans Lynch.

The drugs sail from South America to be unloaded in Central America before being transported across Mexico by powerful cartels into the United States.

Operation Martillo and other military assistance to Central American nations represent one of the most ambitious US efforts against drug cartels since World War II.

The United States has trained security forces across the region, deployed 200 Marines in Guatemala and built forward operating bases in Honduras and shared radar intelligence with Honduran authorities.

But top US generals warned last month that the effort could be greatly undermined by budget cuts.

The cost of international operations and support to nations worldwide to fight drugs went from $2.7 billion in 2001 to $5.7 billion last year.

General John Kelly, head of US Southern Command, told US lawmakers that between 150 and 200 tons of cocaine had been seized last year before reaching the shores of Central America -- seizures amounting to 20 percent of the drugs heading to US cities.

Kelly said automatic budget cuts that went into effect this month could deprive him of the surveillance planes, ships and other resources needed to stem the flow of illegal drugs.

"If I lose those assets, if they go to zero as some are predicting, all of that cocaine and more, I would predict, will get ashore and be on the streets of New York and Boston very, very quickly," he warned.

-- 'Very dangerous road to travel' --

At least four US Navy ships patrol the Pacific ocean and the Caribbean sea at all times, with the backing of six surveillance aircraft.

Mike Vigil, a former chief of the US Drug Enforcement Administration's international operations, said the sea operation was a "good tactic" because seizures are bigger when drugs are intercepted early, before they are broken up into smaller packages on land.

But other experts see limits to the militarization of the drug war and voice concern about the risk of abuses by armies with dark histories of military dictatorship and human rights violations.

"You can't focus solely on the military point of view," said Mark Schneider, vice president of the International Crisis Group think tank.

"If there is anything that the United States should have learned over the course of the past decade, it is that the fundamental response to the threat from transnational crime and the drug cartels has to be strengthening civilian law enforcement institutions in both the transit countries, Guatemala, Honduras, increasingly also Salvador, as well as Mexico," he said.

Adam Isacson, a security expert at the Washington Office on Latin America policy group, said the military is not trained for law enforcement.

"The last time those countries' militaries played a day-to-day role patrolling the streets and being in constant contact with the population, able to search and interrogate citizens... things went very, very badly," he said.

"Those institutions aren't reformed. We are worried that they would go very badly again," he said.

The United States had to stop some of its operations in Honduras last summer after Honduran pilots shot down two airplanes suspected of carrying drugs that were detected by US radars.

A few months earlier, four people were killed in another operation in which DEA agents participated in the Honduran jungle. The families of the targets said they were innocent bystanders.

"Militaries are not designed for law enforcement and as a result they are not trained how to deal with communities," Schneider said, adding that troops frequently use "too much force and they may not have sufficient intelligence to distinguish between the good guys and the bad guys."

"The result as we have seen in the past has been frequently human rights abuses," he said. "So it is a very dangerous road to travel."