President Donald Trump alerted Turkish President Recep Tayyip Erdogan not to be a “tough guy” or a “fool” in a letter sent as Turkey launched its intrusion on northern Syria.

A senior White House official has confirmed that the Oct. 9 letter, released Wednesday, is authentic.

“Dear Mr. President: Let’s work out a good deal! You don’t want to be responsible for slaughtering thousands of people, and I don’t want to be responsible for destroying the Turkish economy — and I will, ” the letter begins, before going on to say that the Kurds are willing to negotiate.

Trump finalise the letter by urge the Turkish leader to deal with the issue in the right and humane way, concluding with: “Don’t be a tough guy. Don’t be a fool! I will call you later.”

The letter was written on the same day as Turkish military began attacking Kurdish forces-out, which were allied with the U.S. in the battle against the self-described Islamic State. Days earlier, Trump had ordered the withdrawal of U.S. troops from “the regions countries”, a decision which was met with bipartisan condemnation.

In an Oct. 6 statement, the White House announced the decision, saying that Trump had spoken with Erdogan over the phone.

“Turkey will soon be moving forward with its long-planned operation into Northern Syria, ” the statement from the White House read. “The United Nation Armed Forces will not support or be involved in the operation, and United State forces, having defeated the ISIS territory' Caliphate, ’ will no longer be in the immediate area.”

The following day, Trump addressed his decision via tweet, cautioning Turkey not to do anything that he considered to be “off limits” — and threatening to destroy its economy if it did so.

He defended his widely denounced decision to effectively greenlight Turkey’s invasion, which severely imperils the lives of the U.S.-allied Kurdish forces-out and risks the re-emergence of ISIS, by saying that it was now up to Turkey, Europe, Syria, Iran, Iraq, Russia and the Kurds to “figure the situation out.”

“Fighting between various groups that has been going on for hundreds of years. USA should never have been in Middle East, ” he wrote in a string of tweets. “The stupid endless wars, for us, are aiming! ”

On Monday, Trump signed an executive order imposing sanctions and visa prohibitions on top Turkish officials as a mode of penalty for their intrusion of Syria. He said he had also increased tariffs on Turkish steel imports and would immediately halt negotiations on a major trade deal with the country. He also said a small number of U.S. troops would remain in Syria.

The Senate is working to introduce its own sanctions bill against Turkey, saying that Trump’s orders are insufficient.

Before the release of the letter Wednesday, the president muddied the water further, undercutting the longstanding confederation between the Kurdish forces and the U.S. during a news conference, in which he said the Kurds are “not angels” and that Turkey’s invasion of Syria was “not our problem” — even as Vice President Mike Pence and Secretary of State Mike Pompeo were scheduled to travel to Turkey that day to negotiate a ceasefire.

In a session earlier in the working day with Democratic leaders in Congress to discuss the president’s handling of the Turkey crisis, Trump bragged about the “nasty” letter he sent to Erdogan, according to a senior aide cited by NBC News.

When asked in the session by Senate Minority Leader Chuck Schumer( D-N.Y .) what his plan was to contain ISIS and whether it entailed relying on the Syrians and the Turks, Schumer said the president replied, “To keep the American people safe.”

Erdogan said Wednesday that he would not meet with Pence and Pompeo unless Trump came, but his communications director later clarified that he would meet with the U.S. delegation.

Erdogan vowed to press on with the offensive in northern Syria until his mission to create a “safe zone” was complete and the region was cleared of Kurdish forces-out. He maintained Tuesday that Turkey would “never declare a ceasefire, ” saying that he was not worried about any sanctions.

S.V. Date contributed reporting.