Former Mexican President Vicente Fox has not made a secret of his dislike of President-elect Donald Trump. In February, when Trump was a late-night punchline who no one thought could actually become president, Fox was already speaking up against the candidate. And now he is addressing Trump directly through the president-elect’s favorite outlet—Twitter.

Fox started out by talking about one issue that unites pretty much all Mexicans: the wall. As he has said before, Fox wrote that “I am not paying for that fucken wall” and called on Trump to “be clear with US tax payers.”

TRUMP, when will you understand that I am not paying for that fucken wall. Be clear with US tax payers. They will pay for it. — Vicente Fox Quesada (@VicenteFoxQue) January 6, 2017

Fox’s tweet came shortly after Trump insisted once again that Mexico would reimburse the United States for the cost of the border wall (or border fence?). After reports that Trump was talking to lawmakers about funding the planned wall, the president-elect took to Twitter on Friday to say that “any money spent on building the Great Wall (for sake of speed), will be paid back by Mexico later.”

The dishonest media does not report that any money spent on building the Great Wall (for sake of speed), will be paid back by Mexico later! — Donald J. Trump (@realDonaldTrump) January 6, 2017

Surely, Trump won’t like it one bit. Another time Fox used similar language to describe the wall, Trump demanded he apologize.

FMR PRES of Mexico, Vicente Fox horribly used the F word when discussing the wall. He must apologize! If I did that there would be a uproar! — Donald J. Trump (@realDonaldTrump) February 25, 2016

Fox added in another tweet that “Trump may ask whoever he wants,” but there was no way Mexico would “pay for his racist monument.”

Trump may ask whoever he wants, but still neither myself nor Mexico are going to pay for his racist monument.

Another promise he can't keep. — Vicente Fox Quesada (@VicenteFoxQue) January 6, 2017

So far, Fox was just repeating the message he has been uttering for months. But then, for his final tweet, Fox hit Trump with the latest intelligence report about how Russia worked to help get him elected and combined that with one of his favorite topics: Trump’s loss of the popular vote. “Sr Trump,the intelligence report is devastating,” he wrote. “Losing election by more than 3M votes and in addition this.Are you a legitimate president?”

Sr Trump,the intelligence report is devastating.Losing election by more than 3M votes and in addition this.Are you a legitimate president? — Vicente Fox Quesada (@VicenteFoxQue) January 6, 2017

So, yes, guess that’s the brave new world of 2017—world leaders duking it out on Twitter.