Mexico City (CNN) On the day before his 77th birthday, Mexican billionaire Carlos Slim said he was celebrating, not his birth, but the unity of his country.

The world's fourth-richest person, according to Forbes, on Friday entered a standing-room-only press conference in the same building from which he runs his empire, holding a set of papers with handwritten notes and a book with several pages marked, titled: "Great Again: How to Fix our Crippled America," by Donald Trump.

With camera lights flashing, the investor sat down at a table, alongside his two sons and his son-in-law for a rare press conference, and began a pep talk that led to a wide-ranging discourse on economic development.

"This meeting was a reason for joy and happiness and emotion, to see how all Mexico has joined together, " he said.

Slim praised his country for solidarity at a time when the country is applauding its President, Enrique Peña Nieto, for canceling a scheduled meeting with US President Trump.

The leader decided not to meet with Trump after the US President tweeted, "If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting."

The last time Slim met with Trump was in December at the President's Mar-a-Lago estate in Florida. He described the dinner meeting as three-on-three. Slim was accompanied by his son-in-law and spokesman. Trump wasn't alone, either.

"Meal was very cordial," he said. "He's got great estimation for Mexico and the importance of having a solid country as a neighbor, the importance of having more economic activity. There's interest that things work, but he has talked about the inconvenience of commercial deficit."

Businessman sees opportunities for Mexico

Slim has studied Trump's actions and words.

He hasn't finished reading the President's book, but he is taking notes.

After holding up the well-worn paperback to the crowd of reporters, he urged others to read it as a way to understand the new American leader. After thumbing through a few pages, Slim quoted directly from the book to explain why Trump's governing principles may not always be politically correct.

Trump's strategy, according to Slim, is to shock and provoke. But in the end, Slim said, Trump's "not a terminator, he's a negotiator."

The businessman believes Trump is attempting to transform the United States, and says this could be an opportunity for Mexico, its economy and its workers.

"What President Trump signifies for us is a big change, a big change in politics and we need to make adjustments in this new civilization," he said.

The change, he says, is favorable for Mexico. "The engineer," as others refer to him, doesn't think Mexicans will end up paying for a wall, especially if Trump's plan is to use a tax on goods coming into the United States.

"The taxes would be paid, not by Mexico, but by those who import and those who are going to be the users."

'Twitter is not a way to negotiate'

When it comes to trade, Slim believes Mexico's relationships with its trading partners are strong and have potential to grow, especially with Asia.

"China has moved from agriculture and rural society, from that to new society that is industrialized and technologized and they have take 20 to 30 million people out of poverty to take them to those great levels of education."

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Trade and a wall are no reason to get angry, he says. It's a reason to negotiate. While he declined to offer advice to Trump or Peña Nieto, Slim offered a small piece of advice on negotiations.

"Twitter is not a way to negotiate. Glad they were able to talk over the phone."

While Trump and Peña Nieto are both avid Twitter users, you won't see Slim engaging in that conversation. The billionaire doesn't own a Twitter account.