UPDATE 1-Mexico does not expect U.S. to designate drug cartels terrorists -minister

(Adds comment by Mexico's foreign minister and president, background on recent violent episodes)

MEXICO CITY, Nov 25 (Reuters) - Mexico's foreign minister, Marcelo Ebrard, said on Monday he did not expect the United States to designate Mexican drug cartels as terrorist groups to allow Washington to intervene south of the border to combat them.

The minister was speaking a day after a formal petition was posted on the White House's website that seeks to designate unspecified Mexican drug cartels as "terrorist organizations."

"I don't think the United States will pursue this path because we're working together, and I don't think they would want to open up the possibility of Mexico invoking the same legal principles," Ebrard told reporters.

Mexican media reported that the White House petition was linked to the massacre earlier this month of three mothers and six children of dual U.S.-Mexican nationality in an ambush by suspected cartel gunmen in northern Mexico.

Ebrard said that in the event drug gangs were designated as terrorists it could, under U.S. law, enable the United States to act directly against the threat if it so chose.

U.S. President Donald Trump responded quickly to the massacre of the women and children, who came from families of U.S. Mormon origin that settled in Mexico decades ago. He urged Mexico to join him in wiping out the drug cartels.

Mexico invited the FBI to cooperate in the investigation to find the killers, and local media reported that dozens of vehicles from the bureau entered the country this month.

Still, Trump's response stirred fears he could exploit the cartel violence to put pressure on Mexico during his bid for re-election next year, just as he did over illegal immigration in his first tilt for the presidency.

Speaking alongside Ebrard, President Andres Manuel Lopez Obrador said Mexico had to resolve its own security problems and would never accept any intervention from abroad.

For its part, Mexico has pressed the United States to classify the August shooting of 22 people, including eight Mexican citizens, in El Paso, Texas, as an act of terrorism.

The White House petition will need some 100,000 signatures by Dec. 24 in order to trigger a written response from the Trump administration, though it would not require any specific action. (Reporting by Dave Graham in Mexico City Editing by Chizu Nomiyama and Matthew Lewis)