President Donald Trump warned Turkish President Recep Tayyip Erdoğan not to be a “fool” in a letter sent shortly after his decision to withdraw U.S. troops from Syria.

The president indicated during a joint press briefing with his Italian counterpart on Wednesday that he had sent a letter to Erdogan urging the Turkish leader not to invade Syria and attack the Kurds. A copy of the letter, which was obtained by Fox Business’ Trish Regan, reveals that Trump threatened to destroy the Turkish economy if Erdogan ignored his warnings.

“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,” Trump wrote.

EXCLUSIVE: I have obtained a copy of ⁦@realDonaldTrump⁩’s letter to #Erdogan. ⁦@POTUS⁩ warns him to not “be a tough guy! Don’t be a fool!” Says he could destroy Turkey’s economy if #Syria is not resolved in a humane way. Details tonight at 8pm #TrishRegan #FoxBusiness pic.twitter.com/9BoSGlbRyt — Trish Regan (@trish_regan) October 16, 2019

“History will look upon you favorably if you get this done the right and humane way,” the president continued. “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!”

Members of both parties have blamed Trump’s withdrawal of troops from northern Syria for Erdogan’s decision to invade Syria, but Trump has defended the decision, asserting that the U.S. should not be involved in conflicts that do not involve them directly. (RELATED: Trump Defends Leaving Syria, Says The Kurds Are ‘No Angels’)

“If Turkey goes into Syria, it is between Turkey and Syria. It’s not our problem,” Trump told reporters during a Wednesday pool spray in the Oval Office. “If Russia wants to get involved with Syria, that’s really up to them. They have a problem with Turkey. They have a problem at a border. It’s not our border, we shouldn’t be losing lives over it.”

Trump authorized sanctions against Turkey earlier this week and re-lifted steel tariffs to 50% in response to Turkey’s aggression against the Kurds.