President Trump is telling Mexico’s president elect that he wants to renegotiate the North Atlantic Free Trade Agreement (NAFTA) “quickly” and warning of a “different route” otherwise.

“I believe a successful renegotiation of [NAFTA] will lead to even more jobs and higher wages for hard-working American and Mexican workers—but only if it can go quickly, because otherwise I must go a much different route,” Trump said in a letter to Mexican President-elect Andrés Manuel López Obrador. “It would not be my preference, but would be far more profitable for the United States.”

The letter was dated July 20, but released on Tuesday night by López Obrador. Trump drafted the letter in response to a letter López Obrador sent to Trump.

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NAFTA has been in effect since 1994, but Trump views the free trade pact as an unfair deal that benefits Mexico more than the U.S.

The U.S., Canada and Mexico have been renegotiating the deal, but talks have been slow.

López Obrador, who will be the country’s first leftist president in decades after the July 1 election, outlined several steps his administration would take to encourage development on the Mexican side of the border, such as raising the minimum wage and matching the local tax rates to that of the states in the U.S. side.

Keeping NAFTA and improving development is seen as a way to stem the flow of economic migrants coming to the United States from Mexico, a common goal for both administrations.

López Obrador said in his letter, sent to Trump with Secretary of State Mike Pompeo who visited Mexico on July 13, that his administration will work “so that no Mexicans have to migrate because of poverty or violence.”

Both Trump and López Obrador also exchanged pleasantries — a sign that the pair might find common ground. Political watchers have also drawn comparisons between the two populists.

“We both achieved electoral success by providing a clear vision for making our countries stronger and better,” Trump said in his letter.

“A stronger relationship will lead to a much stronger and more prosperous Mexico, which frankly would make me very happy!” he added.

Mexican Economy Minister Ildefonso Guajardo is set to meet on Thursday with U.S. Trade Representative Robert Lighthizer. Guajardo has hinted a NAFTA deal could be reached by August.

Speaker Paul Ryan (R-Wis.) said in April the parties needed to reach an agreement by that month for Congress to pass it before November’s midterms.