President Donald Trump had a testy call with Mexican President Enrique Peña Nieto on the subject of Trump’s proposed border wall, according to transcripts of presidential telephone conversations posted Thursday by The Washington Post.

The call was Trump’s first to Nieto from the White House. He was particularly angry that Nieto had made public statements saying that Mexico had no plans to pay for the wall — something that Trump asserted would be possible on the presidential campaign trail.

Trump also described the wall as “the least important thing we are talking about,” but that “politically this might be the most important.”

From the Post report:

Trump described his vow to charge Mexico as a growing political problem, pressuring the Mexican leader to stop saying publicly that his government would never pay.

“You cannot say that to the press,” Trump said repeatedly, according to a transcript of the Jan. 27 call obtained by The Washington Post. Trump made clear that he realized the funding would have to come from other sources but threatened to cut off contact if Mexican President Enrique Peña Nieto continued to make defiant statements.

The funding “will work out in the formula somehow,” Trump said, adding later that “it will come out in the wash, and that is okay.” But “if you are going to say that Mexico is not going to pay for the wall, then I do not want to meet with you guys anymore because I cannot live with that.”

He described the wall as “the least important thing we are talking about, but politically this might be the most important.”

As the call went on, Trump cited a more pleasant call that he’d had earlier in the day:

“Putin was a pleasant call,” Trump said, referring to Russian President Vladi­mir Putin. “This is ridiculous.”

The still-unbuilt wall has been a sore subject for those concerned about the president’s policies on immigration. And since Jan. 27, a federal investigation has been launched into potential Russian interference in the 2016 presidential race and how that might have benefitted Trump.

To read the full text of the Nieto call, click here.