correspondent matt gutman is on the texas border tonight. >> reporter: gridlock tonight at one of the busiest american border crossings in el paso, with millions along the 2,000-mile-long border waiting to see if president trump follows through on his threat to shut down the border if mexico doesn't stop the flood of asylum seekers heading to the u.s. >> and if they don't stop them, we're closing the border. we'll close it. and we'll keep it closed for a long time. i'm not playing games. >> reporter: customs and border patrol estimates more than 100,000 migrants were stopped at the border in march alone. an even higher number expected in april. el paso typically sees a million cars and about 70,000 trucks cross over these bridges into el paso every single month. now, the last time that these bridges were closed for any reason -- over three decades ago. tonight, the chamber of commerce predicts, quote, "an unmitigated economic debacle" if the president carries out his threat, warning 5 million