'Don't be a tough guy': President Trump sent threatening letter to Turkish President Erdogan on day of invasion

Trump asked Erdogan not to slaughter thousands of people.

President Donald Trump admonished the president of Turkey in a surreal personal letter sent last week in which he threatened to be "responsible for destroying the Turkish economy" and said his fellow leader should not be "a tough guy" or a "fool."

The letter was first reported by Fox News and later confirmed as accurate to ABC News by a senior administration official.

In the letter, Trump asks Turkish President Recep Tayyip Erdogan not to slaughter thousands of people and threatens to destroy the Turkish economy.

He closes the letter by stating, "History will look upon you favorably if you get this done the right and humane way. I will look upon you forever as the devil if good things don't happen. Don't be a tough guy. Don't be a fool! I'll call you later."

This letter was dated just three days after the White House sent out a statement announcing that the U.S. would pull forces from the region and the Turkish operation would begin. That statement made no objection to the incursion.

The president has faced bipartisan criticism for the Turkey-Syria conflict, after his decision to pull back U.S. troops ahead of a Turkish operation against U.S.-backed Syrian Kurdish forces.

Trump has since called for a ceasefire and peace settlement. Vice President Mike Pence, Secretary of State Mike Pompeo and National Security Adviser Robert O'Brien are headed to Turkey to meet with officials there.

Many are weighing in on the letter on social media, with some expressing incredulity at its authenticity, and others expressing concerns for the political ramifications.

"This Trump letter to Erdogan is the most damaging correspondance that could’ve been leaked ahead of VP Pence’s visit to Ankara tomorrow," tweeted Soner Cagaptay, the director of the Turkish Research program at The Washington Institute for Near East Policy. "Now, Erdogan has no option but to delay ceasefire in Syria less he be humiliated in front of his nation as weak and bowing to America’s threat."

ABC News' John Parkinson, Mariam Khan, Conor Finnegan and Justin Fishel contributed to this report.