Publicado en The Sydney Morning Herald.

Mexico City: Mexican President Andres Manuel Lopez Obrador used his first full day in office to double down on promises to deploy the military for public security, tackling a key concern: stemming rampant violence and rising murders.

Speaking on Sunday, before rows of generals at a sun-drenched military installation in one of Mexico City's trendier neighbourhoods, Lopez Obrador said the retooling of the military was "indispensable" to tackle the daunting task of making Mexico safer.

The plan requires a constitutional reform that would allow the marines and Army to form a National Guard to police much of the country. Mexico's Supreme Court last month struck down a controversial law signed last year that created a similar legal framework, ruling that the measure was an unconstitutional attempt to normalise the use of the armed forces in public safety.

Deep-rooted corruption and ineffectiveness among police forces has led Mexico to rely heavily for years on the military to combat drug cartels in parts of the country. But both human rights groups and military commanders have long expressed uneasiness about this open-ended policing mission.

Erika Guevara Rosas, Americas director for Amnesty International, has called militarised security a "failed model" that has led to "serious human rights violations at the hands of the armed forces."

Hopes for change are running high among the more than 30 million Mexicans who voted for Lopez Obrador in a sweeping July 1 election victory that also gave his party a majority in Congress. At the same time, worries are mounting among critics who see an expanding authoritarian streak.

If three or four more legislators defect to his Morena party, it would have a super-majority needed to pass constitutional reforms.

Gustavo Madero, a leading senator with the opposition National Action Party, said he was very concerned that bills could quickly make their way through Congress with little input from affected parties or public debate.

"We are going to raise attention to the political costs of the democratic abuses, and that is where we are going to be able to achieve some concessions," said Madero, whose great-uncle was a martyred Mexican president who Lopez Obrador admires and mentions almost daily.

Lopez Obrador says he will put the question of creating a National Guard to a referendum so that the people can weigh in on the decision, as they did with the question of whether to continue with construction of a $US13 billion ($17 billion) airport for the capital that was a third built.

Little more than 1 per cent of registered voters participated in the airport referendum, with a majority calling to halt the project. The peso and Mexican stocks plunged in response.

Valeria Moy, director of the Mexico, Como Vamos? think tank, called such referendums "authoritarianism in disguise" because the questionnaires can be tailored to validate executive proposals.

Madero described the referendums as "simulations of direct democracy" to legitimise decisions that the executive branch has already taken.

Lopez Obrador vowed on the campaign trail to return troops to the barracks rather than to continue deploying the military in domestic matters. He has since backtracked on that promise, saying he didn't realise how hopelessly corrupt civilian law enforcement agencies were.

Plus, the mission is critical: the national statistics institute logged 31,174 slayings in 2017, the most since comparable records began being kept in 1997, including the peak year of Mexico's drug war in 2011. The homicide rate last year broke down to 25 per 100,000 inhabitants - near the levels of Brazil and Colombia at 27 per 100,000.

Lopez Obrador pledged on Sunday to strengthen the armed forces while promoting programs to get more young people to study or work rather than succumbing to the temptation of joining criminal groups. And he praised the generals for having climbed the ranks from working-class beginnings, noting that several were sons of shopkeepers and farmers.

"The soldier, the marine, is the people in uniform," the President said, repeating an oft-used refrain.

AP