Former President Donald Trump on Monday said he would order Mexican President Claudia Sheinbaum to stop the flow of illegal migrants across the U.S. border or face a 25% tariff on their goods.

Mr. Trump previewed the Day 1 demand as part of a riff on plans to crack down on the border invasion and deport migrants. He said Ms. Sheinbaum, who took office on Oct. 1, seems like a nice woman but he hasn’t met her.

“I’m going to inform her on Day 1 or sooner that if they don’t stop this onslaught of criminals and drugs coming into our country, I’m going to immediately impose a 25% tariff on everything they send into the United States of America,” Mr. Trump told supporters in Raleigh, North Carolina. “You’re the first ones I’ve told it to — congratulations, North Carolina.

“If that doesn’t work, I’ll make it 50 [percent]. And if that doesn’t work I’ll make it 75. They’re ripping us off left and right.”

Mr. Trump is locked in a statistical polling tie with Vice President Kamala Harris ahead of Tuesday’s final day of voting. The race will likely be decided by tens of thousands of votes in swing states like North Carolina.

Mr. Trump urged supporters in the Raleigh rally to “close it out” on Election Day, pointing to favorable battleground polls while warning voters not to take anything for granted.

North Carolina is the quintessential purple state, with a Democratic governor and GOP-led legislature. But Democratic presidential candidates haven’t won North Carolina since Barack Obama in 2008, with Mr. Trump victorious in the last two cycles.

Ms. Harris is desperately trying to increase turnout among Black and young voters in the cities and suburbs to counter an impressive rural turnout machine that’s served the GOP well in recent cycles.

Polling averages show Mr. Trump leading by 1 or 2 points in the Tar Heel State, making the race a statistical tie.

“I know North Carolina is gonna make the difference; I can feel it,” said warmup speaker Alina Habba, a lawyer who represented Mr. Trump in two civil cases that he lost this year in New York.

Mr. Trump held a pair of rallies in North Carolina on Saturday, in Gastonia and Greensboro, while Ms. Harris visited Charlotte over the weekend.

Mr. Trump’s tariff plans for Mexico reflect his top issues on the campaign trail — the economy and illegal immigration.

The former president says tariffs will force companies to onshore operations and benefit American workers while funding U.S. programs, though some economists say the levies will be passed along to consumers instead of being absorbed by foreign countries.

Ms. Harris says the tariffs would be a sweeping tax on Americans who can ill afford the added costs.

Mr. Trump says to look at his tariffs during his White House years, when the levies caused hardly any inflation while drawing billions of dollars from China and other countries.