President-elect Donald Trump is upset that the “dishonest” media won't report as fact that Mexico will pay for a border wall. No such deal is in place. (Evan Vucci/AP)

Mexico has not agreed to pay for a wall along its border with the United States. In fact, Mexican President Enrique Peña Nieto has vowed that his country will never fund such a barrier.

Yet President-elect Donald Trump seems to think the media ought to state as fact that Mexico will indeed finance the project. Trump kicked off his Friday by tweeting that the media is “dishonest” because it refuses to report a deal that hasn't happened yet — and won't ever happen, according to Mexico.

Trump's frustration appears to stem from coverage of an effort by congressional Republicans to construct a wall using taxpayer dollars, rather than money from Mexico.

“This is an important tweet because obviously a centerpiece of Donald Trump's successful campaign was, 'I'm going to build the wall and have Mexico pay for it,' " Trump senior adviser Kellyanne Conway said Friday on Fox News. “That hasn't changed, but Congress is examining ways . . . to have the wall paid for through their auspices, and then Mr. Trump is making the point — the president-elect is making the point — that he will have Mexico pay it back.”

“I think the tweet was engendered by people in the media — the 'dishonest media,' as Donald Trump calls them — making the suggestion that he's going back on a campaign promise,” Conway added. “That is not true. He is going to build that wall, and Mexico is going to pay for it. That hasn't changed.”

Clearly Trump is confident that he will (a) succeed in building the wall and (b) compel Mexico to reimburse the United States for the cost. Good for him. And, if he turns out to be right, everyone who said it won't happen will eat their words.

But, at the moment, payment by Mexico is far from a sure thing. It would make zero sense for the media to report that “any money spent . . . will be paid back” because there is no such agreement in place.

Trump told The Washington Post last April that he plans to pressure Mexico to pay up through actions that could hurt the country's economy. Measures include prohibiting Mexican nationals who work in the United States from sending money to relatives at home, imposing tariffs on Mexican imports and canceling visas of Mexicans living in America.

The press has covered Trump's proposal with a high degree of skepticism.

“The feasibility of Trump's plan is unclear both legally and politically, and it would test the bounds of a president's executive powers in seeking to pressure another country,” The Post's Robert Costa and Bob Woodward wrote at the time.

Journalists are not the only ones who doubt that Trump will secure a multibillion-dollar payment from Mexico.

“I don't think Mexico is going to write a check out and say, 'Here, pay for the wall,' " Trump surrogate Ben Carson conceded in a September interview on Fox News.

In a Washington Post-ABC News poll conducted that same month, 76 percent of voters said they think Trump will fail to make Mexico pony up. A majority of Republicans, 52 percent, said he will fail, and even 44 percent of Trump's own voters didn't believe in him.

Trump has a lot of convincing to do — starting with Mexico — if he wants the media to report that money for the wall is definitely going to come from south of the border.