WASHINGTON/MEXICO CITY (Reuters) - U.S. President Donald Trump said he will designate Mexican drug cartels as terrorist groups for their role in trafficking narcotics and people, prompting a speedy request for talks by Mexico.

U.S. President Donald Trump speaks as he meets with Bulgaria's Prime Minister Boyko Borissov in the Oval Office of the White House in Washington, U.S. November 25, 2019. REUTERS/Tom Brenner

“They will be designated ... I have been working on that for the last 90 days. You know, designation is not that easy, you have to go through a process, and we are well into that process,” Trump said in an interview aired on Tuesday with conservative media personality Bill O’Reilly.

Soon afterwards, Mexico’s foreign ministry issued a statement saying it would quickly seek a high-level meeting with U.S. State Department officials to address the legal designation as well as the flow of arms and money to organized crime.

“The foreign minister will establish contact with his counterpart, Michael R. Pompeo, in order to discuss this very important issue for the bilateral agenda,” the ministry said.

Once a particular group is designated as a terrorist organization, under U.S. law it is illegal for people in the United States to knowingly offer support and its members cannot enter the country and may be deported.

Financial institutions that become aware they have funds connected to the group must block the money and alert the U.S. Treasury Department.

Earlier this month, Trump had offered in a tweet to help Mexico “wage WAR on the drug cartels and wipe them off the face of the earth” in the aftermath of the bloodiest attack on U.S. citizens in Mexico for years.

Three women and six children of dual U.S.-Mexican nationality were killed in the ambush in northern Mexico. Mexican authorities said they may have been victims of mistaken identity amid confrontations among drug gangs in the area.

Alex LeBaron, a former Mexican congressman and relative of some of the victims, on Twitter rejected the idea of a U.S. “invasion”.

“We have already been invaded by terrorist cartels,” he wrote. “We demand real coordination between both countries... both countries are responsible for the rising trade in drugs, weapons and money.”

The LeBaron extended family has often been in conflict with drug traffickers in Chihuahua and victims’ relatives said the killers must have known who they were targeting.