CHICAGO (Reuters) - The U.S. Drug Enforcement Administration and Mexican authorities are planning on Wednesday to announce a new strategy to combat transnational Mexican drug cartels that will include a crackdown on their finances, a DEA official said.

Details of the plan will be made at a joint news conference in Chicago on Wednesday afternoon, the official said. The official said representatives from Mexico’s current government would be present but did not name them.

Mexican President-elect Andres Manuel Lopez Obrador, a left-leaning nationalist, has vowed to shake up Mexico’s war on drug cartels after he takes power in December. He wants to rewrite the rules, aides have said, suggesting negotiated peace and amnesties rather than a hardline strategy that critics say has only perpetuated violence.

However, a change of direction without the United States could increase friction between the neighbours, who have been often at loggerheads since Donald Trump became U.S. president.

Trump has irked Mexico with demands that it pay for a border wall and his comments that it does nothing to slow illegal immigration. He has also pushed to revamp the North American Free Trade Agreement (NAFTA) to favour the United States.

But despite difference with the Trump administration on migration and trade issues, officials and security experts in the United States have applauded long-running bilateral efforts to crack down on drug gangs.

For the past 12 years, Mexico has fought the violent cartels by deploying thousands of police, soldiers and intelligence officers.

Mexico remains the principal highway for cocaine to the United States and has become the top source of heroin, which is fuelling a surge in opioid addiction in the United States.