President Donald Trump announced Tuesday that he will designate the powerful Mexican drug cartels as terrorist organizations, allowing the United States government to take decisive action against the narco-organizations.

Speaking with former Fox News host Bill O'Reilly, Trump said, "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," he explained, Reuters reported.

Trump, however, did not elaborate on specifics, but suggested that U.S. action is meant to help topple the cartels.

Designating the cartels as terrorist organizations is a powerful measure. Under U.S. law, it is illegal to knowingly support designated terrorist organizations, and people associated with designated organizations are barred from entering the U.S. Financial institutions are also prohibited from doing business with designated organizations.

Mexican President Andrés Manuel López Obrador's administration was "caught off-guard" by the announcement, the New York Times reported. Mexico's foreign ministry said in a statement they want to meet with senior-level U.S. diplomats "as soon as possible" to discuss Trump's actions.

Some worry that designating the cartels as terrorist organizations will damper U.S.-Mexico relations, specifically in economic and trade matters.

Arturo Sarukhan, the former Mexican ambassador to the U.S., told the Washington Post that former Presidents Barack Obama and George W. Bush also considered formally designating the cartels, but backed down after learning of the harmful impacts such action could have on U.S.-Mexican relations.