A top White House official said Sunday that President Donald Trump is "deadly serious" about imposing tariffs on imports from Mexico, but acknowledged there are no concrete benchmarks being set to assess whether the U.S. ally is stemming the migrant flow enough to satisfy the administration.
"We intentionally left the declaration sort of ad hoc," Mick Mulvaney, the acting White House chief of staff, said on "Fox News Sunday."
"So, there's no specific target, there's no specific percentage, but things have to get better," Mulvaney said. "They have to get dramatically better and they have to get better quickly."
The president said last week that he will impose a 5% tariff on Mexican goods on June 10 to pressure the government of Andres Manuel Lopez Obrador to block Central American migrants from crossing the border into the U.S.
Trump said the import tax will increase by 5% every month through October, topping out at 25%.