A new letter has cast light on Donald Trump's unconventional approach to foreign relations.
Critics of US President Donald Trump have branded a letter he sent to Turkish President Recep Tayyip Erdogan as "juvenile" and "irresponsible" diplomacy.
On Thursday, a 9 October correspondence emerged, in which Mr Trump warned Mr Erdogan about the consequences of invading northern Syria.
After US forces abruptly left the region last week, Turkish forces began attacking long-time Kurdish rivals across the Turkey-Syria border.
"Don't be a tough guy. Don't be a fool!" Mr Trump said in the letter, which the White House has confirmed is real.
"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," he wrote.
"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."
He signed off with, "I will call you later".
But as soon as the letter emerged, reaction ranged from confusion to ridicule.
Some, including a CNN host, questioned if it was real.
While others made fun of the president's approach.
And some on social media said it signalled the commander in chief was unfit for office.
Turkey has made the most of a power vacuum left by the abrupt US departure by invading Kurdish-held territory in neighbouring Syria, already killing hundreds and forcing thousands to flee.
Mr Erdogan claimed the incursion is to combat rival Kurdish militants and create a buffer zone that he can send Syrian refugees back to.
Facing stinging criticism at home, Mr Trump this week slapped sanctions on top Turkish officials and imposed punitive tariffs on Turkish imports.
But on Thursday, the US House of Representatives overwhelmingly condemned Mr Tump's actions in a rare bipartisan rebuke.
A total of 129 members of Mr Trump's Republican Party joined Democrats as the House denounced the withdrawal of US troops from northern Syria in a 354-60 vote.
Additional reporting: AFP