Minnesota Sen. Amy Klobuchar, one of the two-dozen Democrats vying for the party's presidential nomination, denounced President Trump's campaign of brinkmanship with Mexico over rising migration from Central America, calling him "threatener-in-chief."

On "Face the Nation" Sunday, Klobuchar accused Mr. Trump of treating American farmers as if they were "poker chips" at "one of his bankrupt casinos."

For days, Mr. Trump threatened to impose tariffs on all Mexican goods traveling across the southern border unless Mexico's government undertook more efforts to reduce migration from Central America, including tightening its border with Guatemala.

On Friday, however, Mexican and U.S. diplomats reached an agreement in principle to stem the flow of families and unaccompanied children from El Salvador, Honduras and Guatemala heading to the U.S.-Mexico border. Last month, the U.S. apprehended more than 133,00 people near the southwestern border — a 13-year high.

Under the agreement, the Mexican government vowed to deploy National Guardsmen to the Guatemala-Mexico border, while the U.S. indicated it would expand the practice of returning non-Mexican migrants who claim asylum at American ports of entry back to Mexico to await their court hearing — a policy known as "Remain in Mexico."

Although Mr. Trump claimed on Twitter that Mexico also agreed to purchase "large quantities" of American agricultural goods as part of negotiations between both countries, the Mexican Ambassador to the U.S. Martha Bárcena Coqui refused to confirm on "Face the Nation" whether her government consented to such a deal.

Klobuchar said the manner through the president forced the Mexican government to start negotiations to avoid the levies was "wrong."

"I think that we should have a consistent strong trade policy that works for everyone in America," she said.