Rebellious police personnel have seized control of a federal police command center in the Iztapalapa borough in Mexico City. (Marco Ugarte/AP)

Mexican President Andrés Manuel López Obrador struggled Thursday to contain an uprising by federal police over the government’s plan to move them into a massive new security force that will crack down on criminal gangs and U.S.-bound migrants.

Hundreds of rebellious police personnel seized control of their national command center on the edge of Mexico City on Wednesday and were still holed up there a day later. Other officers blocked a major highway between the capital and the northern city of Pachuca.

Under one of López Obrador’s most important overhauls, most of the federal police — about 20,000 officers — are to be absorbed into the newly formed National Guard, along with tens of thousands of military police personnel.

The demonstrating officers are angry about cuts in their pay and benefits under the new force, and they are worried that some officers won’t pass compulsory entrance exams for the Guard. They are threatening a national strike.

“This is truly unprecedented,” said Ricardo Márquez, a former senior security and intelligence official.

He said that only two of the seven federal police divisions were involved in the uprising, but that they were the biggest and best-equipped units. “This is affecting the entire federal police,” he said.

The rebellion has not damaged public security, according to the government. A national strike, though, could remove some of Mexico’s best-trained police officers from the streets and possibly even affect operations against undocumented migrants, Márquez said.

The uprising appeared to be one of the biggest challenges yet for López Obrador, a leftist who took office in December after winning election in a landslide. The National Guard is the centerpiece of his strategy to reduce record numbers of homicides and regain control of territory essentially ruled by organized-crime gangs.

Under an agreement reached last month with the Trump administration, the Guard also has been deployed along Mexico’s northern and southern borders to detain undocumented migrants seeking to cross the country en route to the United States. 

López Obrador told reporters Thursday that there was a “dark hand” behind the protests. Alfonso Durazo, his public security minister, said that some of the leaders of the protests weren’t part of the police force — and that a number of them were involved in corruption and even kidnapping.

Durazo said at a news conference that the government would not use force against the rebellious officers. But he refused to back down on the government’s plans for the National Guard. He demanded that striking officers hand over their weapons.

“We repeat our willingness to continue meeting with [police] representatives in a respectful dialogue, in order to find the best solutions” to the labor issues, Durazo said. “Nonetheless, in this process of negotiation, there is absolutely no margin for modifying the requirements to enter the National Guard.”

Federal police officers who did not pass the entrance tests, or did not want to join the Guard, would be offered jobs in other security forces, such as the one that protects public buildings, he said.

Alejandro Hope, a national security analyst, said the standoff could lead to major problems, including mass police desertions. “This could suddenly reduce the size of the National Guard by 20 or 25 percent,” he said.

But if the government yielded, it could be very expensive to provide higher salaries and more benefits to the force. And “the discontent of the federal police could spread to members of the armed forces in the Guard,” he said.

López Obrador views the National Guard as essential in containing violence in a country where local, state and federal police forces are riddled with corruption. But in his rush to set up the new force, officers have received little training. Some of those deployed to the border in recent weeks have complained about having to sleep on the ground or in dirty installations with broken windows.

Francisco Garduño, the head of Mexico’s national migration institute, responded that the officers were “fifis” — posh — angering them further.

The Guard has been controversial because many of its commanding officers come from the military, even though it technically falls under the civilian leadership of the public security ministry.