President Donald Trump kept up his criticism of Mexico on Friday, saying it “has taken advantage of the U.S. for long enough,” as a crisis over border security and trade deepened.

“Massive trade deficits & little help on the very weak border must change NOW!” Trump wrote on Twitter.

On Thursday, Mexican President Enrique Peña Nieto scrapped a planned trip to Washington to meet Trump, who has repeatedly demanded that Mexico pay for a wall on the U.S. border to halt illegal immigration.

Mexico has taken advantage of the U.S. for long enough. Massive trade deficits & little help on the very weak border must change, NOW! — Donald J. Trump (@realDonaldTrump) January 27, 2017

The White House also suggested on Thursday that the United States could impose a 20 percent tax on goods from Mexico to pay for the wall, sending the peso tumbling.

Speaking about the scrapped summit, senior Trump aide Kellyanne Conway on Friday told Fox News that “the relationship was not imploded. This one meeting has been canceled and that was a mutual cancellation.”

In a separate interview on CBS News, she said the tax was one funding possibility and waved off the chance of Mexican retaliation that could cost American jobs, telling CBS News: “They can do what they want.”

“Mexico should pay for that wall because they get an awful lot from this country,” Conway told CBS.

The White House has said its tax proposal is in the early stages.

A plan being weighed by House Republicans would exempt export revenues from taxation but impose a 20 percent tax on imported goods. The idea, known as a border adjustment tax, would be a significant change from current U.S. policy.

Retailers and other businesses that sell imported goods are not keen on the idea, and some lawmakers have expressed concern about its impact on U.S. consumers.

“The costs for everything from groceries, to cars, to office supplies would go up by 20 (percent), making it harder for middle class families to pay for things they need every day,” Senate Democratic Leader Chuck Schumer said in a statement.

On Friday, The Associated Press reported that Trump and Peña Nieto held a telephone call about the wall dispute.

WASHINGTON (AP) — AP Sources: Trump, Mexican President Pena Nieto held hourlong phone call Friday amid dispute over border wall. — Jill Colvin (@colvinj) January 27, 2017

Despite the tumult, Mexico’s Secretary of Foreign Relations Luis Videgaray said in televised remarks Thursday that he had found areas of potential agreement on trade with the Trump administration during talks this week in Washington and that negotiations would continue.

But that insisting that Mexico pay for the wall was “unacceptable” and the 20 percent tax floated by the Trump administration caught the delegation by surprise.

“It is clear we need to be prepared to immediately neutralise the impact of such a measure,” Economy Secretary Ildefonso Guajardo said.

(Reporting by Susan Heavey and Eric Walsh; Additional reporting by Susan Cornwell; Editing by Alistair Bell)