Republican presidential candidate Ron DeSantis pledged to send US special forces into Mexico to destroy fentanyl labs, disrupt cartel operations and stop the lethal drug from crossing the border.

“Yes, I will do it from Day One,” the Florida governor said in response to a question at the first GOP debate in Milwaukee on Wednesday night. “The president of the United States has got to use all available powers as commander-in-chief to protect our country and to protect the people. So when they’re coming across, yes, we’re going to use lethal force.”

A Mexican embassy spokesman said that President Andrés Manuel López Obrador has been clear that the nation categorically rejects any threats of using the US military against the nation’s cartels.

Fentanyl trafficking through Mexico was among the most talked-about issues in the foreign policy discussion at the debate. The anesthetic-turned-street drug has caused tens of thousands of deaths in the US in recent years. President Joe Biden’s Drug Enforcement Administration chief Anne Milgram has described fentanyl as “the single deadliest drug threat our nation has ever encountered.”

In 2019, China moved to declare fentanyl and its precursor chemicals controlled substances at then-President Donald Trump’s urging, but the change ended up diverting more of the trade through Mexico and that nation’s cartels.

Read more: How Fentanyl Made the US Opioid Crisis So Much Worse: QuickTake

“As president, would I use force? Would I treat them as foreign terrorist organizations?” DeSantis said. “You’re darn right I would.”

Democrats seized on the comments.

“The Republicans cheering for war with Mexico are taking the United States down a dark, dangerous path.” Representative Joaquin Castro of Texas posted on X, the platform formerly known as Twitter.

(Updates with additional comment starting in third paragraph.)