LIMA, Peru.- Mexican drug cartels, once regarded mainly as couriers for South American cocaine producers, have spread their powerful tentacles deep into this Andean nation, sowing violence and nourishing the re-emergence of Shining Path guerrillas, authorities say.

Peruvian authorities suspect a Mexican cartel in the killing of a federal judge in July that shocked this nation.

The allegations underscore the presence of Mexican cartels in the multibillion-dollar shadow economy in Peru, the world´s second-largest producer of cocaine, after neighboring Colombia.

"Just like in Mexico, Peruvian institutions are being put to the test," said Gen. Juan Zárate Gambini, Peru´s anti- narcotics czar and head of the National Police. "We´re very concerned about the consequences, and we´re committed to doing everything to defeat the enemy."

Mexican cartels have become the most dominant drug- trafficking organizations in the hemisphere, authorities say. In his first weeks in office, President Calderón has sent thousands of troops and federal police to Michoacán and Tijuana to confront entrenched cartels.

In South America, the Mexican groups are bypassing the Colombians and cutting their own deals with coca farmers in Peru and Bolivia, setting up dozens of tiny state-of-the-art cocaine processing labs inside Peruvian territory, Western diplomats and Peruvian authorities say.

The Mexicans ship cocaine loads by boat to the Mexican coast, then up to the border with California or Texas, with its coveted Interstate-35 northbound corridor, Peruvian officials and experts said. South Texas remains the leading entry area for cocaine smuggled into the United States, according to the U.S. Drug Enforcement Administration.

In addition, Mexican and Colombian scientists working for the cartels have introduced chemical fertilizers that are multiplying coca leaf production up to 1,000 percent per hectare, Peruvian authorities say.

"Instead of producing 300, 400 plants, new chemicals are ... producing 3,000 plants," said Jaime Artesana, a drug policy expert at the Peruvian Economic and Political Institute, an independent research organization. "The Peruvian government has dedicated just 3 percent of its budget to fight the drug problem. That has to change because we need a new strategy to adapt to more powerful Mexican cartels."

U.S. aid to Peru for drug eradication is an estimated US$300 million over the last five years, and the U.S. government has earmarked US$60 million over the next three years for helicopters for counter-narcotics work.

"Drug trafficking transcends all borders," said the U.S. ambassador to Peru, J. Curtis Struble. "No nation is free from its harmful effect, and (it) impacts all sectors of society."

Despite the U.S. support, coca production in Peru has risen almost 40 percent in recent years, partly as a result of eradication efforts in neighboring Colombia, experts say.

Similarly, the Mexican cartel presence continues to grow. Between 2005 and 2006, about 35 Mexican cartel members have been arrested in Peru. Twentyfive remain in jail, Peruvian authorities said.

Others say U.S. drug policy is part of the problem. Kenneth Sharpe, a Latin American political and drug policy expert at Swarthmore College in Pennsylvania, said the U.S. "prohibition policy" has actually fed the rise of powerful criminal organizations.

"U.S. drug policy based on prohibition has nourished the drug wars in Latin America," Sharpe said. "... There´s absolutely no way a prohibition policy will ever work, here in the United States, in Latin America or anywhere else because all prohibition does is perpetuate the drug trade, rising crime and violence."

In Peru, the presence of the Mexican cartels was illustrated in July, when alleged Tijuana cartel hitmen assassinated Federal Judge Hernán Saturno Vergara as he was eating with a nephew at the restaurant near his judicial office, Peruvian authorities said. Saturno was part of a three-judge panel overseeing a major case against alleged members of the Tijuana cartel.

The Tijuana cartel is allied with the Gulf cartel and its enforcers, the Zetas - who have been blamed for surging violence along the Texas-Mexico border and have been linked to drug killings in North Texas.

The attack on the judge stunned Peruvians and served as a wake-up call on the presence of Mexican cartels in Peru, authorities say.

"The (Tijuana) cartel´s message to authorities was very clear: Messing with us will cost you your life," said Ricardo Valdés, a former Peruvian interior minister and now head of the economic research organization Human and Social Capital. Valdés said the order to kill the judge came from inside the jail where members of the Tijuana cartel were imprisoned.

Zárate, the Peruvian general, said the authorities´ conclusion that Mexican cartels ordered the killing is based on interviews with jailed cartel members.

The Mexican presence has angered President Alan García, Peruvian officials said. García appeared with U.S. President George W. Bush in Washington and pledged "total eradication of the drug trafficker threat."

Peruvian and Mexican authorities held talks in Lima and pledged greater cooperation in fighting drug traffickers.

The implications for this Andean nation of 28 million people are enormous, drug experts say. They point to the violence that has engulfed parts of Mexico and the drug money that has corrupted security forces, judges, journalists and businessmen and is reportedly supporting guerrilla groups.

"We must not allow the violence of Mexico to penetrate Peru," said Gustavo Gorriti Ellenbogen, a Peruvian journalist and author and president of the Press and Society Institute, which promotes media independence.

"Mexico is like one giant bowling alley, with heads rolling," he said, referring to a recent spate of beheadings in Mexico. "We cannot allow that type of violence to happen here."

Meanwhile, the once violent and powerful Maoist guerrilla movement known as Shining Path is regaining strength, thanks largely to drug traffickers, said Peruvian experts, including Valdés and Gorriti. Nearly defunct after the arrest of its leader, Abimael Guzmán, in 1992, the movement is now offering protection to drug traffickers and protecting coca farms from U.S.-backed eradication efforts.

In December, eight suspected Shining Path members were arrested after an attack on a police convoy in a coca-growing region killed five officers and three civilians, including a boy.

"The two remnants of the Shining Path are in the drug-trafficking zone in Alto Huallaga and ... the Apurimac-Ene valley," said Gorriti.

There, Peruvian coca leaves are converted into paste and transported to laboratories in the coastal region for final processing. From there, Mexican cartels, working with Peruvian drug producers, ship the cocaine to not only Mexico and the United States, but also South Africa, the Middle East, Russia, and throughout Latin America, particularly Argentina, Brazil and Chile.

"Eradication measures in Colombia are having an effect, as cocaine production has shifted to Peru," said Artesana of the Peruvian Economic and Political Institute. "But that´s not the only explanation for the growth. It´s also about new and growing markets throughout Europe, Asia and Latin America."

Unlike the guerrillas inside Colombia, the Shining Path movement is now based more on profit than ideology, Gorriti said. "They protect routes and tax drug shipments. That, along with the money they charge ... has provided a source of income which has aided their re-emergence."