MEXICO CITY — President Andrés Manuel López Obrador on Wednesday rejected U.S. suggestions he adopt more aggressive security policies after a massacre of fundamentalist Mormons in northern Mexico, saying that approach has been a “disaster” in the past.

The barbaric killing Monday of three women and six children of the extended LeBaron family — dual U.S.-Mexican citizens — has raised pressure on López Obrador’s leftist government, which has pledged to use social programs to address the root causes of violence.

“It’s unfortunate, sad, because children died. This is painful,” López Obrador said during his regular morning news conference Wednesday. “But trying to resolve this problem by declaring a war? In our country, it’s been shown that this doesn’t work. This was a disaster.”

He was referring to the U.S.-backed offensive against drug groups launched in 2006, with the deployment of the Mexican army to battle organized-crime groups. Around 200,000 people have died in violence related to the conflict.

Mexico continues to work closely with the U.S. government in pursuing drug kingpins. President Trump, however, suggested a more aggressive approach on Tuesday, tweeting that “this is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth. We merely await a call from your great new president!”

Other American politicians have also expressed alarm at the surging violence south of the border.

Sen. Tom Cotton (R-Ark.) said Tuesday that “the Mexican government can’t handle this.”

The Mexican leader’s strategy “may work in a children’s fairy tale,” Cotton told Fox News. “But in the real world... the only thing that can counteract bullets is more and bigger bullets.”

López Obrador responded that Cotton’s comments reflected “his vision.”

“We respect it, but we don’t share it,” the president said.

Mexican authorities noted pointedly on Wednesday that the bullets used in the attack were .223 caliber, produced by Remington, a U.S. firm. Those bullets are typically used in M-16 and AR-15 assault rifles.

Alfonso Durazo, Mexico’s public security minister, noted that 70 percent of all the weapons tied to a crime in Mexico were smuggled from the United States. “That’s why the cooperation of the U.S. government will be fundamental to get good results,” he said.

Foreign Minister Marcelo Ebrard said Wednesday that all results of the investigation would be shared with U.S. authorities, since the case involves American citizens. He said Mexico was open to accepting assistance from the FBI. “The extent of the participation by the FBI or other U.S. institutions (in the investigation) will depend on what the attorney general’s office determines,” he said.

Asked about the effect of the massacre on U.S.-Mexico relations, Ebrard said he did not expect it would raise tensions. The LeBaron clan “is a binational community, and we will act together,” he said. He pledged “immediate actions to clarify what happened.”

The government has said that Monday’s attack may have been a case of mistaken identity, with an organized-crime group thinking the families’ SUVs belonged to a rival. Some relatives of the victims have rejected that idea, saying that the attackers realized the victims were women and children.

Local authorities say various armed groups are fighting for control of the rural area, a channel for shipping drugs to the United States. They include groups connected to the Sinaloa cartel, the Juarez cartel and the Jalisco New Generation cartel.

López Obrador has created a 70,000-strong National Guard, but it has been unable to halt widespread organized-crime violence. Mexico is likely to hit a record level of homicides this year.

Critics say the National Guard hasn’t been used strategically to contain violence, and instead has been spread around the country handling a variety of tasks, including detaining unauthorized migrants heading for the U.S. border.

Alejandro Hope, a security analyst, noted that as of Oct. 14, the National Guard had 3,799 forces in Mexico City. In comparison, it had just 4,126 forces in Sinaloa and Chihuahua, which represent 21 percent of the national territory. The killings of the LeBaron family occurred near the border of the two states.

“If this force serves any purpose, it should be for territorial control, to ensure a presence of the state where it’s almost impossible to add police, to patrol local streets and unattended areas, to fight gunmen and thieves in remote areas of the country,” he wrote in the daily El Universal.

Sonora state authorities reported on Tuesday that they were investigating a man detained on Tuesday with multiple weapons and two hostages, to see if he was connected to the massacre.

Durazo said Wednesday that it appeared the detainee “is not connected to the aggression against the LeBaron family.”