MEXICO CITY (Reuters) - Support for Mexico’s president has fallen some ten percentage points during a surge in gang-related violence, a poll showed on Friday, just as the U.S. ambassador voiced concern about “parallel government” by cartels in parts of the country.

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The Nov. 6-11 survey of 1,000 Mexicans for newspaper El Universal showed President Andres Manuel Lopez Obrador had an approval rating of 58.7%, down from 68.7% in late August. The poll had a margin of error of 3.1 percentage points.

Although Lopez Obrador’s popularity remains strong compared with many world leaders, nearly one year into his administration, skepticism is growing about his performance on the back of several shocking security lapses to recently roil Mexico.

Last month the president took flak from critics when it emerged security forces had released a son of the notorious kingpin Joaquin “El Chapo” Guzman after heavily-armed cartel gunmen overwhelmed security forces and briefly took control of the northern city of Culiacan.

That criticism was compounded by outrage and condemnation of the government from some U.S. lawmakers when suspected cartel gunmen massacred three mothers and six children of dual U.S.-Mexican nationality in northern Mexico last week.

U.S. President Donald Trump has responded by suggesting Mexico should join the United States to fight the cartels, fueling concerns that the American leader could use gang violence to put pressure on the Mexican government as he has over migration.

Speaking on Thursday, the U.S. ambassador in Mexico City, Christopher Landau, offered a terse assessment of the situation, saying there were parts of Mexico in which drug cartels formed a kind of “parallel government”.

“It can’t be that the territory where they have this kind of power continues to expand across the country,” Landau said on Thursday during an event in the northern city of Monterrey in remarks that were later broadcast on television.

“The future of Mexico is so important that if we don’t fight this now, it’s going to get much worse,” he added.

A dozen years of gang-fueled violence have claimed well over 200,000 lives in Mexico and murders hit record levels last year.

Taking office in December, the veteran leftist Lopez Obrador has pledged to address the root causes of crime and is pursuing a less confrontational approach to pacifying the country.

He quickly created a new militarized police force, or National Guard, to tackle the problem. But at the behest of Trump, thousands of its members have been sent to the borders of Mexico to help contain illegal immigration from Central America.