The U.S. military is preparing to send about 1,000 additional active-duty troops to the border with Mexico, a U.S. official said, just two days after President Donald Trump signed an executive order on immigration.

U.S. officials say the Pentagon will begin deploying as many as 1,500 active duty troops to help secure the southern border in the coming days.

Mexican drug gangs are a driving force behind the U.S. fentanyl crisis and Trump vowed to crack down on cartels during his successful presidential campaign.