MEXICO CITY – Mexico’s president scrapped a planned summit with Donald Trump on Thursday in the face of insistent tweets from the US president demanding Mexico pay for a border wall, a spat that threatens Mexican efforts to salvage trade ties.

Trump had been scheduled to receive Pena Nieto at the White House next week, for their first meeting since the inauguration. Instead, the Republican president is facing a foreign policy spat during his first week in the Oval Office.

But their escalating war of words over who would fund the proposed border wall — a central pledge made by Trump during his successful presidential campaign — escalated to a breaking point on Thursday.

“If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting,” Trump said on Twitter in the morning.

“We informed the White House this morning that I will not attend the working meeting scheduled for next Tuesday” with Trump in Washington, the Mexican leader responded on Twitter.

“Mexico reiterates its willingness to work with the United States to reach agreements in both nations’ interests.”

White House spokesman Sean Spicer told reporters that the “lines of communications” would remain open and Washington hoped to “schedule something in the future.”