U.S. President Donald Trump has warned Turkish President Recep Tayyip Erdoğan in a letter about Turkey’s incursion into Syria, saying “Don’t be a tough guy” and “Don’t be a fool!”

The Oct. 9 letter was obtained by a Fox Business reporter on Oct. 16 as Trump battled to control the political damage following his decision to pull U.S. troops out of northern Syria, clearing the way for the Turkish offensive against Washington’s Kurdish allies.

The letter tried to persuade Erdoğan to reverse a decision to launch a military offensive in Syria that Erdoğan told Trump about in an Oct. 6 phone call.

“Let’s work out a good deal!” Trump said. “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.”

“I have worked hard to solve some of your problems. Don’t let the world down. You can make a great deal,” he said in the letter.

Turkey launched its military offensive, dubbed Operation Peace Spring, in northeastern Syria on Oct. 9 with the aim of clearing the area of Kurdish-led Syrian Democratic Forces (SDF) and setting up a “safe zone” for the return of over one million Syrian refugees.

The leading group in the SDF is the People’s Protection Units (YPG), which is the Syrian affiliate of the Kurdistan Workers’ Party (PKK) – a group that Turkey has been battling for over 30 years.

The PKK is designated as a terrorist organization by Ankara, the U.S. and the European Union.

In the letter, the president wrote that SDF Commander General Mazloum Kobani Abdi was willing to negotiate and to make some concessions.

He said he had confidentially enclosed to Erdoğan a copy of a letter Mazloum had sent him, though the letter didn’t surface.

“History will look upon you favorably if you get this done the right and humane way. It 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!” said Trump.

He added: “I will call you later.”

Turkish officials acknowledged the authenticity of the letter, while also slamming it.

“This letter that was penned on Oct. 9 was rejected by President Erdoğan and it was trashed. The clearest answer given to this letter is Operation Peace Spring that began on Oct. 9,” presidential sources told CNN Türk on Oct. 17.

Trump: Syria may have some help with Russia, and that’s fine

Since the announcement of the decision to pullout U.S. troops from Syria, Trump has been under fire from both Republicans and Democrats.

Upon U.S. withdrawal, the SDF has reached a deal with the Syrian army, which was brokered by Russia.

The withdrawal has allowed Syrian President Bashar al-Assad to redeploy his forces to an area that had been beyond his control for years in the more than eight-year Syrian war.

Syrian troops accompanied by Russian forces entered the city of Kobani, a strategically important border city and a potential flashpoint for a wider conflict, the UK-based Syrian Observatory for Human Rights, which monitors the Syrian war, reported.

Lebanon’s al-Mayadeen TV reported that Russian-backed Syrian forces had also set up outposts in Raqqa, the one-time capital of ISIS’ so-called caliphate, which the Kurds captured in 2017 at the peak of their campaign with U.S. support.

Earlier on Oct. 16, Trump said he did not mind Russia helping Syria in a conflict with Turkey and rejected criticism of his withdrawal of U.S. troops, calling it “strategically brilliant.”

Speaking to reporters as he met Italian President Sergio Mattarella and then at a joint news conference, Trump said the Kurds were “not angels” and that it might be necessary for Russian-backed Syria and Turkey to “fight it out.”

“Our soldiers are not in harm’s way – as they shouldn’t be, as two countries fight over land that has nothing to do with us,” Trump said during Oval Office talks with Mattarella.

“I viewed the situation on the Turkish border with Syria to be for the United States strategically brilliant,” Trump said.

“Syria may have some help with Russia, and that’s fine. It’s a lot of sand,” he later said. “So you have Syria and you have Turkey. They’re going to argue it out, maybe they’re going to fight it out. But our men aren’t going to get killed over it.”

Russia questions language of ‘unusual’ Trump letter

Meanwhile, the Kremlin on Oct. 17 questioned the tone of Trump’s letter, saying it was highly unusual for correspondence between heads of state.

“You don’t often encounter such language in correspondence between heads of state. It’s a highly unusual letter,” Kremlin spokesman Dmitry Peskov told reporters on a conference call.

Eyes on Pence, Erdoğan meeting

Washington announced sanctions on Oct. 14 to punish Turkey, but Trump’s critics said the steps, mainly a steel tariffs hike and a pause in trade talks, were too feeble to have an impact.

On Oct. 16, U.S. Treasury Secretary Steven Mnuchin said sanctions included the entire ministries of energy and defense and could be broadened to others. Republicans in the U.S. House of Representatives also plan to introduce sanctions legislation.

Trump dispatched some of his top aides, including Vice President Mike Pence and Secretary of State Mike Pompeo to Turkey for emergency talks to try to persuade Ankara to halt its assault.

Trump said he thought Pence and Erdoğan would have a “successful meeting,” saying if they did not, U.S. sanctions and tariffs “will be devastating to Turkey’s economy.”

Erdoğan’s spokesman said Turkey’s Foreign Ministry was preparing retaliation for U.S. sanctions.

A White House meeting between Trump, Republican and Democratic lawmakers on U.S. policy in Syria was cut short. Pelosi, the top Democrat in Congress, said Trump was upset by a 354-60 House vote condemning his Syria withdrawal. Republicans said Pelosi “stormed out.”

“What we witnessed on the part of the president was a meltdown. Sad to say,” Pelosi, whose fellow Democrats are investigating whether to impeach Trump because of his actions toward Ukraine, said upon leaving.

Trump shot back via Twitter late on Oct. 16, posting – “Nervous Nancy’s unhinged meltdown!” with a photo of Pelosi standing up and pointing at him during the meeting.

Dozens of Republicans joined the majority Democrats in the House vote. The split underscored deep unhappiness in Congress over Trump’s action, which many lawmakers view as abandoning Kurdish fighters who had been fighting alongside U.S. troops to defeat ISIS.

Trump has denied giving a green light to Turkey.

Erdoğan has insisted there will be no ceasefire, and said he might call off a visit to the United States in November because of the “very big disrespect” shown by U.S. politicians.

Senior Republicans voiced dismay.

“I’m sorry that we are where we are,” Senate Majority Leader Mitch McConnell said, telling reporters he hoped Pence and Pompeo “can somehow repair the damage” during their trip to Ankara.