WASHINGTON-President Donald trump warned Turkish President Recep Tayyip Erdogan “not to be a tough guy” in a letter to his counterpart before Ankara launched a deadly invasion in Northern Syria. 

The October 9 letter, confirmed by a senior administration official, struck an unusually casual tone for correspondence between two foreign leaders discussing Turkey’s plans to invade the restive region. It came three days after Erdogan told Trump of his plans to launch an offensive against Kurdish forces, many of whom have been fighting alongside us forces against the Islamic state (ISIS) terrorist group in Northern Syria.

After a phone call on October 6, the President announced his intention to withdraw troops from Syria, clearing the way for Turkey to invade Syria and prompting a rare bipartisan condemnation on Capitol hill.

“Let’s work out a good deal! You don’t want to be responsible for killing thousands of people and I don’t want to be responsible for destroying the Turkish economy – and I will,” trump wrote.

Trump called on Erdogan to carry out his offensive in a humanitarian way, but refused to delineate what exactly that entails.

“Don’t let the world down,” he said, adding that he had assurances from General Mazlum Kobani, commander of the U.S. – backed Syrian democratic forces (SDF), that he would make concessions ahead of the planned assault on Turkey. 

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“History will look at you positively if you get it done right and humanely. He will look at you forever like the devil if good things don’t happen.”

In the last line of the letter, the us President warned: “Don’t be a tough guy. Don’t be a fool! I’ll call you later.

During a press conference with Italian President Sergio Mattarella on Wednesday, trump referred to the letter, arguing that he did not give Erdogan the “green light” to invade Syria when he decided to withdraw U.S. troops from the region. 

The administration has repeatedly stressed in recent days that trump does not approve of the Turkish invasion in an attempt to control the political fallout of the President’s decision to withdraw from Syria, but a White house statement about his phone conversation with Erdogan did not mention a warning against it.

Facing mounting pressure from both sides of the aisle, trump announced on Monday a new round of sanctions against Turkey for invading Syria, calling for an immediate ceasefire in the region. 

Vice President Mike Pence and Secretary of state Mike Pompeo are traveling to Ankara to try to negotiate a ceasefire and allay fears of a humanitarian crisis. Erdogan told reporters Wednesday that he declined to meet with Pompeo and Pence, but an aide later declined to comment. 

The house, meanwhile, voted 354-60 on Wednesday to approve trump’s rare bipartisan rebuke of the situation. Two-thirds of Republicans joined Democrats to support the measure. 

After the resolution was passed, Democrats walked out of the White house meeting on Syria, saying President Donald trump insulted House speaker Nancy Pelosi and launched a “diatribe.”

Read more: trump Administration imposes sanctions on Turkey as critics criticize decision to withdraw U.S. troops

The President has repeatedly framed his decision in Syria as part of his broader pledge to withdraw U.S. troops because of foreign entanglements.

But U.S. troops remained in Syria on Wednesday despite trump’s announcement that they had withdrawn, according to a U.S. official who was not authorized to speak publicly. The military continues to close outposts in Syria, home to U.S. special forces, the official said. The military is concerned about its security as Turkish-backed militias are seen as a potential threat in Syria to U.S. troops being evacuated by planes and convoys.

It is unclear how many of the 1,000 troops trump intends to withdraw from Syria will return to the U.S. and ferry them to other countries in the region.  

Mark Dubowitz, Executive Director of the Foundation for the defense of democracies, said that while the letter is fodder for political satire, it raises questions about why trump did not threaten sanctions in his initial conversation with Erdogan.

“President trump sent this letter three days after the phone conversation with Erdogan and on the day when Turkish troops were on the move. Aside from his remarkable language, which would make for great political satire if the consequences were not so dangerous, it raises the obvious question: Why not warn the Turkish leader of these consequences before he invaded Syria as a deterrent, rather than after when it was too late?