By Catherine Bremer

TAMPICO, Mexico, Oct 19 (Reuters) - The Mexican army convoy rolled off a Hercules plane in the middle of the night, purred through this sweltering port city's dingy back streets and swooped on traffickers unloading cocaine in a warehouse.

Shipped to Mexico hours before in a container labeled "bread flour", the 11.7 tonnes seized last week was Mexico's biggest-ever cocaine bust and led to the arrest of a string of police and customs officers thought to be in on the deal.

It capped a flurry of high-profile seizures this year, a triumph that officials put down to better intelligence and more anonymous tip-offs from a public sick of drug violence.

The U.S. government is delighted by the latest raids in northeastern Mexico, controlled by the entrenched Gulf cartel. and plans to give $1.5 billion to help Mexico's anti-drugs war.

President Felipe Calderon deployed 25,000 troops last December to back up police in fighting the cartels, whose tit-for-tat murders have spiraled out of control.

Welcome as the cash will be, alongside the $7 billion Calderon is putting in, Mexican officials say the leap in drug seizures and arrests shows they are already making progress.

What they really need from the United States, they say, is a crackdown on its huge market for illicit drugs and on the arms dealers who keep Mexico's cartels flush with everything from handguns to rocket-propelled grenades.

"If there are no weapons, there's no violence. These arms aren't from Mexico, they're from the other side," Gen. Javier del Real Magallanes, head of the army drug operation for northeastern Mexico, told Reuters in an interview this week.

He said U.S. aid would buy more surveillance and detection equipment, but would not make a major difference on its own.

"We lack technology, technology is expensive. We also need the United States to do what it should with respect to arms trafficking... We have to put a brake on the sale of arms," said the general, whose remit covers the northeastern states of Nuevo Leon, Tamaulipas and San Luis Potosi.

In those three states, the army has seized twice as many weapons so far this year as in the past four years combined.

The most powerful arms confiscated are from the United States, including 350 U.S. army grenades, del Real Magallanes said.

KILLINGS TRIGGER TIP-OFFS

Calderon's offensive in drug hotspots has failed to curb bloody turf wars, mainly between the Gulf Cartel and rivals from the state of Sinaloa. Killings this year have already overtaken last year's 2,100.

Once confined to the border area and away from the public eye, drug violence has shifted south to stain the beach resort of Acapulco and quiet cities like Veracruz. Hitmen leave out severed heads and tortured corpses for television cameras.

Polls show that most Mexicans support the crackdown.

"It seems to be working. They've captured a lot of drugs and narcos," said Isabel Pantoja, 58 and a mother of six, at her home in a run-down neighborhood near the raided warehouse in Tampico, part of the Gulf cartel's northeastern domain.

"It's more dangerous than before, the narcos are very bold. But they must carry on or all our kids will be drug addicts."

Officials say the violence has emboldened Mexicans to phone or e-mail the authorities when they see suspicious activity. Each arrest boosts intelligence, triggering more swoops.

Busts like that in Tampico, and the September capture of 3.3 tonnes of cocaine in a crashed plane in southern Mexico, also lift public confidence in the authorities, which have for decades been seen as weaker than wealthy drug lords.

"It was immense," said Porfirio Castillo, local police chief for the area where the Tampico raid took place. "But this is only beginning. It's going to take time."

Hundreds of arrests this year include senior cartel members, one picked up dining in a Mexico City steakhouse, and several others have been extradited to the United States.

The Gulf Cartel has suffered some of the most telling blows and its boss Osiel Cardenas was extradited in January.

The clampdown has hit the gangs' smuggling operations and driven up cocaine prices on U.S. streets but it also means more drugs stay in Mexico. Tampico residents say it's now routine to be offered cocaine in the bars by the port.

And U.S. security consultants Stratfor warned in a report this week that the bloodshed is not over. "Despite the government's efforts, the cartels -- not the authorities -- control the level of violence."

Del Real Magallanes said violence would only be curbed by keeping the pressure on. "It's impossible to think we can end all this, but we can curb their power and put a brake on the violence."

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