Mexico just keeps getting deadlier.

Even as President Felipe Calderón dispatched more than 24,000 military and security forces to pacify areas overrun by drug gangs, the country saw more than 2,500 deaths related to the drug trade in 2007.

Mexico has logged important successes, from extraditions to drug seizures, and Mr. Calderón's administration has been lauded by many observers as the boldest in recent history in the face of organized crime. On Monday, officials announced the arrest of one of Mexico's top operatives, a suspected leader of the infamous Sinaloa cartel.

But with each victory comes another daylight shootout, another federal agent down, and a heightened perception that the problem is bigger than Mexico can solve alone.

So far, the administration has refused to back down and increasingly is appealing to the US for support.

A new rhetoric of "shared responsibility" between the two nations was underscored by the recent visit of US Attorney General Michael Mukasey in Mexico. While the cooperation generates suspicion among those who worry that the US will seek to impose its own interests, many say a bilateral approach is critical if Mexico is to come out from under the deluge of drug violence.

"This is the new perspective of both the Mexican and US governments," says Erubiel Tirado, director of the national security program at the Iberoamerican University in Mexico City. "But the Mexican state must define the bilateral agenda, not just the American agenda."

Violence flaring up in Tijuana

Some of the most recent violence has flared in Tijuana, just south of San Diego. Last week, a federal agent was killed in a shootout that played out in range of schoolchildren.

Earlier in the week, a police commander was murdered at home, along with his wife and daughter.

President Calderón has vowed to press on. "It is possible to win the battle for public security, " Calderón said earlier this month. "But to achieve that, we must remain united."

In fact, many say that the spikes in violence are a result of increased pressure on the drug lords – and that it will get worse before it gets better, especially if the first $500 million of a potential $1.4 billion US aid package known as the Merida Initiative is approved to assist in enforcmeent.

"Should the Merida Initiative go through, it's not overnight that the Mexican government, in conjunction with the US, will defeat organized crime," says Armand Peschard-Sverdrup, an expert on Mexico and head of the Washington-based consulting firm Peschard-Sverdrup & Associates. "This is a protracted process, and I think in the short term there will be a natural pushback from organized crime."

Cartel vs. cartel

The growing violence in Mexico is largely attributed to battles between the major drug groups operating in Mexico, including the Sinaloa and Gulf cartels, and the fracturing that has taken place as leaders are arrested and factions have vied to assert control over lucrative smuggling routes.

Violence has even spilled over to the US. This weekend, a US Border Patrol agent was killed by a suspected drug smuggler when he tried to stop their fleeing Hummer.

The US has hailed the Calderón administration's efforts. In response to the arrest of the alleged Sinaloa cartel leader, Alfredo Beltrán Leyva, US Ambassador Tony Garza said in a statement: "When Mexico takes dangerous criminals like Beltrán Leyva and his crew off the streets, the people of the United States also benefit."

US Attorney General Mukasey pledged to help stop the flow of US guns into Mexico, which has long been blamed for the spectacular gun wars that often break out across this country.

He said US authorities are giving their Mexican counterparts more access to electronic databases to help trace weapons and plan to introduce a Spanish edition of the database soon.

Not all observers welcome a heavy hand from the north. Mr. Tirado says that cooperation is crucial, but worries that Mexico is reacting to what the US wants. "If you do not have a bilateral perspective, and are only following the north, you are not taking an integral approach," he says.

Many also want greater focus on mid-term objectives, such as rooting out corruption, improving the judicial system, and lessening demand for drugs in the US and, increasingly, Mexico.

"If we are not looking at the causes of the violence, the problems will not go away," says Jose Maria Ramos, a security expert at the research institute Colegio de la Frontera Norte in Tijuana.