WASHINGTON – After promising Americans on the campaign trail that Mexico would pay for a multi-billion dollar border wall, then subsequently telling the president of Mexico that he understood Mexico wouldn’t really pay for it, President Donald Trump is back to claiming that Mexico will pay for it.

Somehow.

“One way or the other Mexico is going to pay for the wall,” Trump said Monday at a joint news conference with Finnish President Sauli Niinistö.

What that method is remains just as hazy as it was during Trump’s 17-month presidential campaign. At times his aides suggested Mexico would pay for it through new tariffs or with a tax on remittances sent back to Mexico. But for the most part, Trump just promised his crowds that he would build a wall along the southern border and force Mexico to pay for it, often engaging them in a call and response: “Who’s going to pay for the wall?” he would ask, with the audience screaming back: “Mexico!”

Yet seven days after taking office, Trump told Mexican President Enrique Peña Nieto that he understood that Mexico wouldn’t actually pay for the wall, but asked Peña not to say that publicly because it would cause political problems for Trump with his supporters.

“I have to have Mexico pay for the wall – I have to. I have been talking about it for a two-year period,” Trump told Peña, according to a transcript of the conversation that was leaked to the Washington Post earlier this month. “You cannot say anymore that the United States is going to pay for the wall. I am just going to say that we are working it out.”

Trump returned to the issue on his own at a campaign rally last week, when he promised that he would refuse to approve a new spending bill that does not contain money to start building his border wall. “If we have to shut down that government, we’re building that wall,” he told supporters in Phoenix, Arizona, last week.

That, of course, raised the question: If Mexico was supposed to pay for the wall, why did the U.S. have to face a potential government shutdown over construction money for it?

Trump faced exactly that query Monday, now with the additional twist that a new funding bill could contain money to help victims of Hurricane Harvey but not have money for Trump’s wall. The president said he did not think the issue would force a shutdown, but he still wouldn’t rule out the tactic. “I hope that’s not necessary. If it’s necessary, we’ll have to see,” he said.

The federal government starts a new budget year Oct. 1, but only has congressionally-approved funding to operate through Sept. 30.